Image Forming Apparatus and Developing Cartridge

ABSTRACT

A developing cartridge includes a case having a first sidewall and a second sidewall opposite to the first sidewall, and a developing roller disposed between the first sidewall and second sidewall. The developing roller can include a developing roller shaft and a developing roller member configured to carry a developing agent thereon, the developing roller member disposed around the developing roller shaft. Also, the developing cartridge can include an electrode disposed on the first sidewall adjacent to the developing roller shaft, the electrode electrically connected to the developing roller member, and a driven coupling disposed on the second sidewall. The electrode can include, an extending portion extending in a direction away from the first sidewall. An outermost periphery of the driven coupling defines a projection plane projecting in a direction towards the electrode, wherein at least a part of the extending portion is disposed within the projection plane.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of prior U.S. application Ser. No.14/974,648, filed Dec. 18, 2015, which is a continuation of prior U.S.application Ser. No. 14/496,217, filed Sep. 25, 2014, which issued Dec.22, 2015, as U.S. Pat. No. 9,217,988B2, which is a continuation of priorU.S. application Ser. No. 14/057,775, filed Oct. 18, 2013, which issuedNov. 11, 2014, as U.S. Pat. No. 8,886,076B2, which is a continuation ofprior U.S. application Ser. No. 13/493,022, filed Jun. 11, 2012, whichissued Apr. 8, 2014, as U.S. Pat. No. 8,693,914B2, which is acontinuation of prior U.S. application Ser. No. 13/213,924, filed Aug.19, 2011, which issued Jul. 3, 2012 as U.S. Pat. No. 8,213,826B2, whichis a continuation of prior U.S. application Ser. No. 12/728,804, filedMar. 22, 2010, which issued Sep. 6, 2011 as U.S. Pat. No. 8,014,694B2,which is a continuation of prior U.S. application Ser. No. 11/456,224,filed Jul. 10, 2006, which issued Apr. 6, 2010 as U.S. Pat. No.7,693,443B2, which is a continuation-in-part of prior U.S. applicationSer. No. 11/391,220, filed Mar. 29, 2006, which issued Apr. 6, 2010 asU.S. Pat. No. 7,693,442B2, which claims priority to Japanese PatentApplication Nos. 2005-200510 filed Jul. 8, 2005, 2005-259644 filed Sep.7, 2005 and 2005-376522 filed Dec. 27, 2005, the entire contents ofwhich are incorporated herein by reference.

TECHNICAL FIELD

Aspects of the invention relate to an image forming apparatus and adeveloping cartridge for use in image forming apparatuses, such as laserprinters.

BACKGROUND

A developing cartridge that generally contains toner is removablyinstalled in a main body of an image forming apparatus, such as a laserprinter. The developing cartridge is provided in its case with a tonerchamber configured to contain toner, an agitator rotatably disposed inthe toner chamber, a supply roller configured to supply the toner, adeveloping roller configured to carry the toner thereon, alayer-thickness regulating blade configured to form a thin layer oftoner on the developing roller.

As the developing cartridge is driven after being installed in the mainbody, the toner in the toner chamber is supplied to the supply rolleraccording to the rotation of the agitator. Thereafter, the toner issupplied to the developing roller in accordance with the rotation of thesupply roller. Then, the toner passes between the layer-thicknessregulating blade and the developing roller in accordance with therotation of the developing roller, and is carried on the developingroller as a think layer. A developing bias is applied to the developingroller. An electrostatic latent image formed on a photoconductive drumis developed by the toner carried on the developing roller.

The developing cartridge includes a gear mechanism configured to drivethe developing roller, the supply roller, and the agitator. For example,Japanese Laid-Open Patent Publication No. 2003-295614 discloses the gearmechanism provided in one sidewall of the case of the developingcartridge. The gear mechanism in the developing cartridge includes aninput gear to which the drive force is input from the main body of theimage forming apparatus.

A bearing member configured to support an end of the developing rolleris provided on the other sidewall of the case of the developingcartridge. The bearing member is integrally formed with a feeding memberconfigured to apply developing bias to the developing roller.

In the developing cartridge disclosed in Japanese Laid-Open PatentPublication No. 2003-295614, a line, parallel to the developing rollershaft, passing through the input gear provided on one sidewall andanother line, parallel to the developing roller shaft, passing throughthe feeding member provided on the other sidewall, are disposed parallelto each other with some distance therebetween. If such rotation ortorsion power is exerted on the developing cartridge that producesrotation or torsion of the developing cartridge about the input gearwhen drive force is input to the input gear from the main body of theimage forming apparatus, the feeding member provided on the othersidewall is placed out of position, resulting in poor power supply orpower feeding from the main body of the image forming apparatus.

SUMMARY

Aspects provide an image forming apparatus and a developing cartridgethat stably feeds or supplies power to a developing roller shaft evenwhen a drive force is directly transmitted from a drive coupling of animage forming apparatus to a driven coupling of the developingcartridge.

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrative aspects will be described in detail with reference to thefollowing figures wherein:

FIG. 1 is a sectional side view of a general configuration of a laserprinter, as an image forming apparatus, according to an illustrativeaspect;

FIG. 2 is a sectional side view of a process cartridge for use in thelaser printer shown in FIG. 1 according to an illustrative aspect;

FIG. 3 is a sectional side view of a drum cartridge for use in the laserprinter shown in FIG. 1 according to an illustrative aspect;

FIG. 4 is a sectional side view of a developing cartridge for use in thelaser printer shown in FIG. 1 according to an illustrative aspect;

FIG. 5 is a perspective view of the developing cartridge viewed from anupper rear left side;

FIG. 6 is a perspective view of the developing cartridge viewed from anupper rear right side;

FIG. 7 is a perspective view of the developing cartridge viewed from alower front left side;

FIG. 8 is a perspective view of the developing cartridge viewed from alower front right side;

FIG. 9 is a plan view of the developing cartridge viewed from the rearside;

FIG. 10 is a plan view of the developing cartridge viewed from the frontside;

FIG. 11 is a plan view of the developing cartridge viewed from the top;

FIG. 12 is a plan view of the developing cartridge viewed from thebottom;

FIG. 13 is a left side view of the developing cartridge with a gearcover attached to the developing cartridge;

FIG. 14 is a left side view of the developing cartridge with a gearcover detached from the developing cartridge;

FIG. 15 is a right side view of the developing cartridge;

FIG. 16 is a perspective view of the drum cartridge viewed from an upperrear left side;

FIG. 17 is a perspective view of the process cartridge viewed from anupper front right side;

FIG. 18A and FIG. 18B provide a perspective view showing a part of adeveloping shaft and a side view of the developing shaft, respectively,according to an illustrative aspect;

FIG. 19 is a left side view of the developing cartridge corresponding toFIG. 13, with a contact plate projected in a width direction of thedeveloping cartridge according to an illustrative aspect;

FIG. 20 is a right side view of the developing cartridge correspondingto FIG. 15, with a driven coupling part projected in the width directionof the developing cartridge according to an illustrative aspect;

FIG. 21 is a perspective view of the developing cartridge, correspondingto FIG. 6, viewed from an upper rear right side, with an electrodemember detached from the developing cartridge according to anillustrative aspect;

FIG. 22 is a perspective view of the developing cartridge, correspondingto FIG. 8, viewed from a lower front right side, with the electrodemember detached from the developing cartridge;

FIG. 23 is a right side view of the developing cartridge, correspondingto FIG. 15;

FIG. 24 is a sectional view of the developing cartridge taken along lineA-A of FIG. 23;

FIG. 25 is a sectional view of the developing cartridge taken along lineB-B of FIG. 23;

FIG. 26 is a perspective view of a color laser printer, as an imageforming apparatus, according to another illustrative aspect of theinvention;

FIG. 27 is a front view of a developing cartridge according to theillustrative aspect shown in FIG. 26;

FIG. 28 is a perspective back view of the developing cartridge shown inFIG. 27;

FIG. 29 is a perspective front view of the developing cartridge shown inFIG. 27;

FIG. 30 is a perspective front view of the developing cartridge shown inFIG. 27;

FIG. 31 is a perspective overhead view of a process cartridge shown inFIG. 26 according to an illustrative aspect;

FIG. 32 is a partially enlarged perspective view of a photoconductiveunit shown in FIG. 31 according to an illustrative aspect;

FIGS. 33A and 33B are perspective views of the photoconductive unitshown in FIG. 31, viewed from a side at an angle;

FIGS. 34A and 34B are perspective views of the photoconductive unitshown in FIG. 31, viewed from a side at an angle opposite to the sideshown in FIGS. 33A and 33B;

FIG. 35A is a side view of the developing cartridge, shown in FIG. 27,in a non-pressing (retracted) state (position);

FIG. 35B is a side view of the developing cartridge, shown in FIG. 27,in a pressing state (position);

FIG. 36A is an enlarged cross-sectional side view of a press actuationmechanism, shown in FIG. 35A, in the non-pressing state (position);

FIG. 36B is an enlarged cross-sectional side view of the press actuationmechanism, shown in FIG. 35B, in the pressing state (position);

FIG. 37A is a side view of the developing cartridge in the press state(position), viewed from a side opposite to the side shown in FIG. 35B;

FIG. 37B is an explanatory schematic showing forces exerted on thedeveloping cartridge in the pressing state (position) shown in FIG. 37A;

FIG. 38 is an enlarged side view showing a periphery of a terminalportion shown in FIG. 37A;

FIG. 39 is an enlarged perspective view showing a periphery of theprocess cartridge shown in FIG. 26 according to an illustrative aspect;

FIG. 40 is an enlarged perspective view showing a periphery of slideguide frames and linear cam mechanisms shown in FIG. 26 according to anillustrative aspect;

FIG. 41 is a perspective view of a pair of bar cam members shown in FIG.40;

FIG. 42A is an enlarged perspective view of a supplemental cam member,shown in FIG. 41, in a turned state;

FIG. 42B is an enlarged perspective view of the supplemental cam member,shown in FIG. 41, in an upright state;

FIG. 43A is an enlarged perspective view of the bar cam member and thesupplemental cam members shown in FIG. 41, wherein the bar cam member isin the foremost position;

FIG. 43B is an enlarged perspective view of the bar cam member and thesupplemental cam members shown in FIG. 41, wherein the bar cam member isin the rearmost position;

FIG. 44 is a cross-sectional side view of the bar cam member and thesupplemental cam members when the bar cam member shown in FIG. 43B is inthe rearmost position;

FIG. 45 is a cross-sectional side view of the bar cam member and thesupplemental cam members when the bar cam member shown in FIGS. 43A and43B is in a middle position;

FIG. 46 is a cross-sectional side view of the bar cam member and thesupplemental cam members when the bar cam member shown in FIG. 43A is inthe foremost position;

FIG. 47 is an enlarged side view of the developing cartridges and thelinear cam mechanisms when the bar cam members shown in FIG. 39 are inthe rearmost position;

FIG. 48 is an enlarged side view of the developing cartridges and thelinear cam mechanisms when the bar cam members shown in FIG. 39 are inthe middle position;

FIG. 49 is an enlarged side view of the developing cartridges and thelinear cam mechanisms when the bar cam members shown in FIG. 39 are inthe foremost position;

FIG. 50 is a bottom view of the developing cartridges and a drive forcetransmission mechanism for transmitting drive force thereto provided ina main body frame shown in FIG. 26 according to an illustrative aspect;

FIG. 51 is a bottom view of the developing cartridges and a drive forcetransmission mechanism for transmitting drive force thereto provided ina main body frame shown in FIG. 26 according to an illustrative aspect;and

FIG. 52 is an enlarged side view showing a modification of a peripheryof the terminal portion shown in FIG. 38.

DETAILED DESCRIPTION

It is noted that various connections are set forth between elements inthe following description. It is noted that these connections in generaland, unless specified otherwise, may be direct or indirect and that thisspecification is not intended to be limiting in this respect.

Illustrative aspects will be described with reference to theaccompanying drawings. FIG. 1 is a sectional side view of a generalconfiguration of a laser printer in which a developing cartridge isinstalled according to an illustrative aspect. FIG. 2 is a sectionalside view of a process cartridge for use in the laser printer shown inFIG. 1 according to an illustrative aspect. FIG. 3 is a sectional sideview of a drum cartridge for use in the laser printer shown in FIG. 1according to an illustrative aspect. FIG. 4 is a sectional side view ofthe developing cartridge for use in the laser printer shown in FIG. 1according to an illustrative aspect.

As shown in FIG. 1, a laser printer 1 includes a main body casing 2, anda feeder unit 4 that supplies a sheet 3 and an image forming unit 5 thatforms an image on the supplied sheet 3. The feeder unit 4 and the imageforming unit 5 are disposed in the main body casing 2.

(1) Main Casing

Formed at a front side of the main body casing 2 (left side in FIG. 1)is an opening 6 through which a process cartridge 20 is inserted into orremoved from the main body casing 2. A front cover 7 for opening andclosing the opening 6 is provided at the front side of the main bodycasing 2. The front cover 7 is pivotally supported by a cover shaft 8,which is inserted into a lower end portion of the front cover 7. Whenthe front cover 7 is pivotally closed about the cover shaft 8, theopening 6 is closed with the front cover 7. When the front cover 7 ispivotally opened about the cover shaft 8, the opening 6 is open. Thus,the process cartridge 20 can be inserted into or removed from the mainbody casing 2 through the opening 6.

In the following description, the side on which the front cover 7 isprovided when the process cartridge 20 is installed in the main bodycasing 2, is defined as the front side of the laser printer 1/processcartridge 20 (including a developing cartridge 30), and the sideopposite to the front side is defined as the rear side.

(2) Feeder Unit

As shown in FIG. 1, the feeder unit 4 is provided, at a bottom portionin the main body casing 2, with a sheet supply tray 9 slidablyinstallable in the main body casing 2 along the front-rear direction, aseparation roller 10 and a separation pad 11 provided at upper front endportions of the sheet supply tray 9, and a pickup roller 12 provided ata rear side of the separation roller 10 (upstream side of the separationpad 11 in a sheet feeding direction). The feeder unit 4 further includesa sheet powder removing roller 13 provided at an upper front portion ofthe separation roller 10 (downstream side of the separation roller 10 inthe sheet feeding direction) and a pinch roller 14 disposed to face thesheet powder removing roller 13.

The feeder unit 4 includes a pair of register rollers 15 disposed belowthe process cartridge 20 when installed, in a sheet feed path downstreamof a U-turned portion thereof that makes a U-turn near the sheet powderremoving roller 13 toward the rear side. Provided inside the sheetsupply tray 9 is a sheet mount plate 16 configured to mount a stack ofsheets 3 thereon. The sheet mount plate 16 is pivotable between amounting position where the sheet mount plate 16 is substantiallyparallel to a bottom plate of the sheet supply tray 9 with a front endof the sheet mount plate 16 at a lower position and a supply positionwhere the sheet mount plate 16 is at an angle with the front end thereofat a higher position.

A lever 17 for raising the front end of the sheet mount plate 16 isprovided at the front end of the sheet supply tray 9. The lever 17 issupported at an underside of the front end portion of the sheet mounttray 16 so as to pivot about a lever shaft 18 disposed at a rear end ofthe lever 17. The lever 17 is pivotable between a parallel positionwhere the front end of the lever 17 is substantially parallel to thebottom plate of the sheet supply tray 9 and an angled position where thefront end of the lever 17 is at an angle to raise the sheet mount plate16. When drive force is input to the lever shaft 18, the lever 17 pivotsabout the lever shaft 18. Accordingly, the front end of the lever 17raises the front end of the sheet mount plate 16 to move the sheet mountplate 16 to the supply position.

As the sheet mount plate 16 is placed in the supply position, anuppermost sheet 3 on the sheet mount plate 16 is pressed against thepickup roller 12, and is fed to a separation position between theseparation roller 10 and the separation pad 11, by the rotation of thepickup roller 12.

When the sheet supply tray 9 is removed from the main body casing 2, thesheet mount plate 16 is placed in the mounting position. As the sheetmount plate 16 is in the mounting position, a stack of sheets 3 can bemounted on the sheet mount plate 16.

The sheets 3 fed toward the separation position by the pickup roller 12are separated one by one when sandwiched between the separation roller10 and the separation pad 11 by the rotation of the separation roller10. The fed sheet 3 passes through a portion between the sheet powderremoving roller 13 and the pinch roller 14 where sheet powders or fibersare removed. Then, the sheet 3 is fed along the U-turned sheet feed pathtoward the register rollers 15.

The register rollers 15 register the sheet 3 or reduce the skew of thesheet 3. Then, the register rollers 15 feed the sheet 3 to a transferposition between a photoconductive drum 28, as a photoconductive member,and the transfer roller 31 where a toner image on the photoconductivedrum 28 is transferred to the sheet 3.

Image Forming Unit

The image forming unit 5 includes a scanner unit 19, the processcartridge 20, and a fixing unit 21.

(a) Scanner Unit

The scanner unit 19 is disposed at an upper portion in the main bodycasing 2. The scanner unit 19 includes a laser light source (not shown),a polygon mirror 22 that is driven so as to spin, an fθ lens 23, areflecting mirror 24, a lens 25, and a reflecting mirror 26. As shown inchain lines in FIG. 1, a laser beam emitted from the laser light sourcebased on image data is deflected by the polygon mirror 22 and passesthrough the fθ lens 23. Then, the laser beam is reflected off thereflecting mirror 24, and directed, through the lens 25, to thereflecting mirror 26 where the laser beam is bent downward toward thesurface of the photoconductive drum 28 of the process cartridge 20.Thus, the surface of the photoconductive drum 28 is irradiated with thelaser beam.

(b) Process Cartridge

The process cartridge 20 is removably installed in the main body casing2 below the scanner unit 19, through the opening 6. As shown in FIG. 2,the process cartridge 20 includes a drum cartridge 27, as aphotoconductive cartridge, and a developing cartridge 30 according to atleast one illustrative aspect, that is removably set in the drumcartridge 27.

(b-1) Drum Cartridge

As shown in FIG. 3, the drum cartridge 27 includes a drum frame 58, andthe photoconductive drum 28, a scorotron charger 29, the transfer roller31 and a cleaning member 32 that are disposed in the drum frame 58.

The drum frame 58 includes an upper frame 141 that supports the charger29 and the cleaning member 32, and a lower frame 142 that supports thephotoconductive drum 28 and the transfer roller 31.

As shown in FIGS. 3 and 16, the lower frame 142 is provided with abottom wall 143, left and right sidewalls 144L, 144R, a front wall 145and a rear wall 146 that are integrally formed so as to open upward. Thebottom wall 143 is of substantially rectangular plate shape. The leftand right sidewalls 144L, 144R are disposed so as to face each other atthe left and right ends of the bottom wall 143. The front wall 145 isdisposed at the front end of the bottom wall 143. The rear wall 146 isdisposed at the rear end of the bottom wall 143.

The front part of the lower frame 142 is defined as a developingcartridge installation portion 147 in which the developing cartridge 30is installed. The rear part of the lower frame 142 is defined as a drumsupporting portion 148 where the lower frame 142 and the upper frame 141face each other in the vertical direction and the photoconductive drum28 is supported.

As shown in FIG. 3, the photoconductive drum 28 includes a cylindricaldrum body 33 having at its outermost surface a positively chargeablephotoconductive layer made from, for example, polycarbonate and themetal drum shaft 34 disposed at an axis of the drum body 33 along anaxial direction of the drum body 33. The drum shaft 34 is supported bythe left sidewall 144L and the right sidewall 144R of the lower frame142. The drum body 33 is rotatably supported on the drum shaft 34. Thephotoconductive drum 28 is driven so as to rotate on the drum shaft 34by the input of the drive force from a motor (not shown) during imageformation.

The scorotron charger 29 is supported by the upper frame 141 at an upperrear portion of the photoconductive drum 28. The scorotron charger 29 isdisposed so as to face the photoconductive drum 28 with a predetermineddistance therebetween, to prevent the scorotron charger 29 fromcontacting the photoconductive drum 28. The charger 29 includes a wire67 disposed to face the photoconductive drum 28 with a predetermineddistance therebetween and a grid 68 disposed between the wire 67 and thephotoconductive drum 28 to control the amount of electric charge fromthe wire 67 to the photoconductive drum 28. During image formation, biasvoltage is applied to the grid 68. At the same time, high voltage isapplied to the wire 67, to generate corona discharge from the wire 67.Thus, the surface of the photoconductive drum 28 is uniformly andpositively charged by the charger 29.

The transfer roller 31 is disposed in the lower frame 142 below thephotoconductive drum 28. The transfer roller 31 contacts thephotoconductive drum 28 in the vertical direction so as to form a nipportion between the transfer roller 31 and the photoconductive drum 28.The transfer roller 31 includes a metal transfer roller shaft 56 coveredby a rubber roller 57 formed of a conductive rubber material. Thetransfer roller shaft 56 is rotatably supported by the left and rightsidewalls 144L, 142R of the lower frame 142. During transfer of thetoner on the sheet 3 (during image formation), drive force is input froma motor (not shown) to rotate the transfer roller 31. A transfer bias isapplied to the transfer roller 31 during transfer of the toner onto thesheet 3.

The cleaning member 32 is supported by the upper frame 141 behind thephotoconductive drum 28 so as to face the drum 28. The cleaning member32 includes a cleaning brush 65 to catch the sheet powders or fibers onthe photoconductive drum 28, and a supporting plate 66 that supports thecleaning brush 65 opposite to the photoconductive drum 28 with respectto the cleaning brush 65 (behind the photoconductive drum 28).

The cleaning brush 65 includes non-woven fabric with many conductivefiber-like brush bristles fixed thereon. The cleaning brush 65 isattached to the supporting plate 66 by double-sided adhesive tape. Thecleaning brush 65 is disposed to contact the photoconductive drum 28.The supporting plate 66 is supported by the upper frame 141 whilesupporting the cleaning brush 65.

The direction parallel to the drum shaft 34 of the photoconductive drum28 may be referred to as the “first direction”. The directionperpendicular to the first direction directed toward the front side ofthe main body casing 2 may be referred to as the “second direction”. Inthe developing cartridge installation portion 147, a handle 149, whichis held during installation or removal of the drum cartridge 27, isformed on the substantially central portion of the front wall 145 in thefirst direction.

Disposed at each end of the front wall 145 with respect to the firstdirection is a pressing lever 150 that presses the developing cartridge30 installed in the developing cartridge installation portion 147 towardthe rear side, to firmly press the developing roller 38 against thephotoconductive drum 28. Each pressing lever 150 is formed of a thickplate and into a substantially triangular shape in side view. The lowerend of each pressing lever 150 is pivotally supported by a fixed shaft(not shown) extending inwardly in the first direction from each sidewall144L, 144R.

A compression spring (not shown) is disposed between each pressing lever150 and the front wall 145. Therefore, each pressing lever 150 is alwayspressed or inclined rearward by an urging force of the compressionspring.

A lock lever 151 is provided on one sidewall (right sidewall 144R) withsome distance between the lock lever 151 and one of the pressing levers150 in the front-rear direction. The lock lever 151 is of substantiallya rectangular shape in side view. The lock lever 151 is provided with aflexible portion 152 extending downward from the lock lever 151. Thelock lever 151 is pivotally supported by the right sidewall 144R withthe flexible portion 152 engaged with a rib (not shown) formed on thebottom wall 143.

Disposed in the developing cartridge installation portion 147 at therear ends of the left and right sidewalls 144L, 144R are guide grooves153 along which a collar member 116 and a developing roller shaftcovering portion 118, which will be described below, are guided toinstall the developing cartridge 30 in the developing cartridgeinstallation portion 147. As shown in FIGS. 2 and 3, formed in thedeveloping cartridge installation portion 147 slightly forward of thecentral portion of the bottom wall 143 in the second direction areinstallation bases 155 on which installation portions 133 of thedeveloping cartridge 30 are placed.

(b-2) Developing Cartridge

As shown in FIGS. 16 and 17, the developing cartridge 30 is removablyinstalled in the developing cartridge installation portion 147 of thelower frame 142 when the process cartridge 20 is separated or removedfrom the main body casing 2. As shown in FIG. 4, the developingcartridge 30 includes a developing frame 36 and a supply roller 37, adeveloping roller 38, and a layer-thickness regulating blade 39 that aredisposed in the developing frame 36.

The developing frame 36 is formed into a box-shape that is openrearward. Disposed in the developing frame 36 are a partition plate 40,and a toner chamber 41 and a developing chamber 42 that are partitionedby the partition plate 40. The partition plate 40 is disposed in themiddle of the developing frame 36 in the second direction, so as todivide the developing frame 36 in the front-rear direction. A port 43 isformed in the middle portion of the partition plate 40 in the verticaldirection.

The toner chamber 41 is defined in an internal space of the developingframe 36 on the front side thereof partitioned by the partition plate40. The toner chamber 41 contains positively chargeable nonmagneticsingle-component toner as a developing agent. The toner is, for example,polymerized toner that is obtained by copolymerizing polymerizablemonomers using a polymerization method, such as a suspensionpolymerization method. The polymerizable monomers may be styrene-basedmonomers, such as styrene, and acrylic-based monomers, such as acrylicacid, alkyl (C1-C4) acrylate, and alkyl (C1-C4) methacrylate. Theparticle of such polymerized toner is of a substantially sphericalshape, and thus the polymerized toner has excellent fluidity andcontributes to high-quality image formation.

The toner is mixed with wax and a coloring agent, such as carbon black,as well as an external additive, such as silica, to improve the fluidityof the toner. Average toner particle sizes are approximately 6 to 10 μm.

A toner filling port through which the toner is supplied into the tonerchamber 41 is formed at left and right sidewalls 69L, 69R (describedbelow) of the developing frame 36 in the toner chamber 41. The tonerfilling port is covered with a toner cap 35, as shown in FIG. 15.

A toner detection window 44 for detecting a residual toner amount isprovided on each of the left and right sidewalls 69L, 69R of thedeveloping frame 36 in the toner chamber 41. The toner detection windows44 are formed on the left and right sidewalls 69L, 69R of the developingframe 36 near the partition plate 40 so as to face each other along awidth direction of the developing cartridge 30 (perpendicular to thefront-rear direction and the vertical direction). Each toner detectionwindow 44 is formed by embedding a transparent disk plate in an openingformed in the left and right sidewalls 69L, 69R of the developing frame36, as shown in FIGS. 13, 14 and 15.

An agitator 45 that agitates the toner in the toner chamber 41 isprovided in the toner chamber 41. The agitator 45 is provided with anagitator rotating shaft 46 and an agitating member 47. The agitatorrotating shaft 46 is rotatably supported by the left and right sidewalls69L, 69R of the developing frame 36 at a substantially central portionof the toner chamber 41. The agitating member 47 is provided on theagitator rotating shaft 46. Drive force from a motor (not shown) isinput to the agitator rotating shaft 46 to rotate the agitator 45 duringdevelopment (during image formation).

The agitator 45 is provided with wipers 48. Each wiper 48 is provided oneach end of the agitator rotating shaft 46 with respect to its axialdirection. When the agitator rotating shaft 46 rotates, each wiper 48pivotally moves about the agitator rotating shaft 46 in acircumferential direction in the toner chamber 41, to wipe off the tonerdetection windows 44 provided on the left and right sidewalls 69L, 69Rof the developing frame 36. Thus, the toner detection windows 44 arewiped off by the wipers 48.

The developing chamber 42 is defined in an internal space of thedeveloping frame 36 on the rear side thereof partitioned by thepartition plate 40. The supply roller 37 is disposed behind the port 43above a central bottom wall 75 (described below). The supply roller 37includes a metal supply roller shaft 50 covered by a sponge roller 51,as a supply roller member, formed of a conductive foaming material. Thesupply roller shaft 50 is rotatably supported by the left and rightsidewalls 69L, 69R of the developing frame 36 in the developing chamber42. Each end of the supply roller shaft 50 extends outward from the leftand right sidewall 69L, 69R. Drive force from a motor (not shown) isinput to the supply roller shaft 50 to rotate the supply roller 37during development (during image formation). The same bias as thedeveloping bias, which is applied to the developing roller 38, isapplied to the supply roller 37 during development (during imageformation).

The developing roller 38 is disposed in the developing chamber 42 behindthe supply roller 37 and above a rear bottom wall 76 (described below),as shown in FIG. 4. The developing roller 38 contacts the supply roller37, so as to apply some pressures to each other. The developing roller38 includes a metal developing roller shaft 52 covered by a rubberroller 53, as a developing roller member, formed of conductive rubbermaterial. The developing roller shaft 52 extends parallel to the supplyroller shaft 50. The developing roller shaft 52 is rotatably supportedby the left and right sidewalls 69L, 69R (described below) of thedeveloping frame 36 in the developing chamber 42.

Each end of the developing roller shaft 52 extends outward from the leftand right sidewall 69L, 69R (described below). The rubber roller 53 isformed of a conductive urethane or silicone rubber including fine carbonparticles. A surface of the rubber roller 53 is coated with urethanerubber or silicone rubber including fluorine. Drive force is input tothe developing roller shaft 52 from a motor (not shown) to rotate thedeveloping roller 38 during development (during image formation). Thedeveloping bias is applied to the developing roller 38 duringdevelopment (during image formation).

The layer-thickness regulating blade 39 includes a blade body 54 formedof metal leaf spring member and a pressing portion 55 that has asemicircular cross-sectional shape and is formed of insulating siliconerubber. The pressing portion 55 is provided at a free end of the bladebody 54. A base end, opposite to the free end, of the blade body 54 ofthe layer-thickness regulating blade 39 is supported above thedeveloping roller 38 in a blade attachment portion 77 (described below)by an attachment member 134. The free end of the blade body 54 extendsobliquely downward and frontward toward the supply roller 37. Thepressing portion 55 is pressed against the developing roller 38 byelastic force of the blade body 54.

(b-3) Development and Transfer Operations

During image formation, drive force from a motor (not shown) is input tothe agitator rotating shaft 46 so that the agitating member 47 ispivotally moved about the agitator rotating shaft 46 in acircumferential direction in the toner chamber 41. Accordingly, toner inthe toner chamber 41 is agitated by the agitating member 47, and isdischarged toward the developing chamber 42, through the port 43 formedin the middle portion of the partition plate 40 in the verticaldirection so as to allow the fluid communication in the front-reardirection.

The toner discharged through the port 43 toward the developing chamber42 is supplied to the rubber roller 53 of the developing roller 38 bythe sponge roller 51 of the supply roller 37, in accordance with therotation of the supply roller shaft 50. At this time, the toner ispositively charged by the friction between the sponge roller 51 of thesupply roller 37 and the rubber roller 53 of the developing roller 38.The toner supplied onto the rubber roller 53 of the developing roller 38passes between the pressing portion 55 of the layer-thickness regulatingblade 39 and the rubber roller 53 of the developing roller 38, inaccordance with the rotation of the developing roller shaft 52. Thetoner is carried on the rubber roller 53 of the developing roller 38, asa thin layer whose thickness has been regulated.

As shown in FIG. 2, while the photoconductive drum 28 rotates, thesurface of the drum body 33 is uniformly and positively charged by thescorotron charger 29. Then, a laser beam from the scanner unit 19 scansacross the surface of the drum body 33 at high speed, thereby forming,on the surface of the drum body 33, an electrostatic latent imagecorresponding to an image to be formed on the sheet 3.

Thereafter, as the toner, which is carried on the rubber roller 53 ofthe developing roller 38 and positively charged, makes contact with thedrum body 33 of the photoconductive drum 28 in accordance with therotation of the developing roller shaft 52, the toner is supplied to theelectrostatic latent image formed on the surface of the drum body 33,that is, parts exposed to the laser beam, where the potential level islower than the remaining part of the drum body 33 surface uniformlypositively charged. Thus, the electrostatic latent image on the drumbody 33 is made visible. Thus, a toner image is formed on the drum body33 by reverse developing.

Then, the toner image carried on the surface of the drum body 33 istransferred onto the sheet 3, with the application of the transfer biasto the rubber roller 57 of the transfer roller 31, while the sheet 3conveyed by the register rollers 15 passes through the transfer positionbetween the drum body 33 and the rubber roller 57 of the transfer roller31. The sheet 3 having the toner image transferred thereon is fed to thefixing unit 21.

The toner remaining on the surface of the drum body 33 after the tonerimage transfer is collected by the rubber roller 53 of the developingroller 38. Sheet powders or fibers attached to the surface of the drumbody 33 after the toner image transfer due to the contact to the sheet3, is removed by the cleaning brush 65 of the cleaning member 32 fromthe surface of the drum body 33 of the photoconductive drum 28.

(c) Fixing Unit

As shown in FIG. 1, the fixing unit 21 is provided behind the processcartridge 20, with some distance between the photoconductive drum 28 ofthe process cartridge 20 and the fixing unit 21 in the substantiallyhorizontal direction. The fixing unit 21 includes a unit frame 59, and aheat roller 60 and a pressure roller 61 that are disposed in the unitframe 59.

The heat roller 60 includes a metal tube whose surface is coated withfluorocarbon resin and a halogen lamp inserted into the metal tube forheat application. The heat roller 60 is rotated by an input of powerfrom a motor (not shown) during fixing (during image formation).

The pressure roller 61 is disposed below the heat roller 60 opposite tothe heat roller 60, so as to press against the heat roller 60. Thepressure roller 61 includes a metal roller shaft covered by a rubberroller formed of a rubber material. The pressure roller 61 is driven bythe rotation of the heat roller 60.

In the fixing unit 21, the toner image transferred onto the sheet 3 atthe transfer position is thermally fixed while the sheet 3 passesbetween the heat roller 60 and the pressure roller 61. The sheet 3having the toner image fixed thereon is conveyed toward a sheet outputtray 62 formed on the top surface of the main body casing 2. A sheetoutput path from the fixing unit 21 to the sheet output tray 62 isformed into a substantially “U” shape, so as to turn toward the frontside from the fixing unit 21. A feeding roller 63 is disposed in thesheet output path. Output rollers 64 are disposed at downstream endportions of the sheet output path.

The sheet 3 that is subjected to the thermal fixing process in thefixing unit 21 is conveyed to the sheet output path. The sheet 3 is fedto the output rollers 64 by the feeding roller 63. Then, the sheet 3 isoutput on the sheet output tray 62 by the output rollers 64.

2. Developing Cartridge

FIG. 5 is a perspective view of the developing cartridge viewed from anupper rear left side. FIG. 6 is a perspective view of the developingcartridge viewed from an upper rear right side. FIG. 7 is a perspectiveview of the developing cartridge viewed from a lower front left side.FIG. 8 is a perspective view of the developing cartridge viewed from alower front right side. FIG. 9 is a plan view of the developingcartridge viewed from the rear side. FIG. 10 is a plan view of thedeveloping cartridge viewed from the front side. FIG. 11 is a plan viewof the developing cartridge viewed from the top. FIG. 12 is a plan viewof the developing cartridge viewed from the bottom. FIG. 13 is a leftside view of the developing cartridge with a gear cover attached to thedeveloping cartridge. FIG. 14 is a left side view of the developingcartridge with a gear cover unattached to the developing cartridge. FIG.15 is a right side view of the developing cartridge. FIG. 19 is a leftside view of the developing cartridge corresponding to FIG. 13, with acontact plate projected in a width direction of the developingcartridge. FIG. 20 is a right side view of the developing cartridgecorresponding to FIG. 15, with a driven coupling part projected in thewidth direction of the developing cartridge.

The developing cartridge 30 will be described in detail below withreference to FIGS. 4-15 and FIGS. 19 and 20.

(1) Developing Frame

As shown in FIGS. 4 and 5, the developing frame 36 includes a pair ofleft and right sidewalls 69L, 69R, an upper wall 70, a bottom wall 71and a front wall 72 that are integrally formed. The developing frame 36is formed into a box shape with a rear opening portion 73 formedthereon.

The left and right sidewalls 69L, 69R are of a flat plate shape. Asshown in FIG. 11, the left and right sidewalls 69L, 69R are disposedopposite to each other in the first direction, so as to interpose thetoner chamber 41 and the developing chamber 42 between the left andright sidewalls 69L, 69R. As shown in FIGS. 14 and 15, the left andright sidewalls 69L, 69R close each end of the toner chamber 41 and thedeveloping chamber 42. As shown in FIGS. 4 and 11, the upper wall 70 isof a flat plate shape. The upper wall 70 is connected to upper ends ofthe left and right sidewalls 69L, 69R, so as to extend between the leftand right sidewalls 69L, 69R. The upper wall 70 closes an upper portionof the toner chamber 41 and the developing chamber 42.

As shown in FIGS. 4 and 7, the bottom wall 71 is of a curved plateshape. The bottom wall 71 is connected to lower ends of the left andright sidewalls 69L, 69R, so as to extend between the left and rightsidewalls 69L, 69R. The bottom wall 71 closes a lower portion of thetoner chamber 41 and the developing chamber 42. The bottom wall 71includes a front bottom wall 74, a middle bottom wall 75, and a rearbottom wall 76 that are integrally formed.

The front bottom wall 74 is formed into a substantially semicircularcross-sectional shape in association with the rotating path of theagitator 45 in the toner chamber 41.

The middle bottom wall 75 is disposed behind the front bottom wall 74.The middle bottom wall 75 is formed into a substantially semicircularcross-sectional shape in association with the supply roller 37 in thedeveloping chamber 42.

The rear bottom wall 76 is disposed behind the middle bottom wall 75.The rear bottom wall 76 is tilted downward from the front side to therear side.

The front wall 72 is of a flat plate shape. The front wall 72 isconnected to front ends of the left and right sidewalls 69L, 69R, so asto extend between the left and right sidewalls 69L, 69R. The front wall72 closes a front portion of the toner chamber 41.

As shown in FIG. 4, the blade attachment portion 77 is provided at anupper rear portion of the left and right sidewalls 69L, 69R between theleft and right sidewalls 69L, 69R. The blade attachment portion 77 isformed into a substantially triangular shape in sectional side view,such that the width of the blade attachment portion 77 becomes narrowertoward the lower side. A rear end face of the blade attachment portion77 is formed as an inclined surface that is inclined obliquely towardthe front side from an upper end to a lower end of the blade attachmentportion 77.

As shown in FIGS. 4 and 9, the base end of the blade body 54 is fixed tothe rear end face of the blade attachment portion 77 by the attachmentmember 134, with a sealing member 135 interposed between the rear endface of the blade attachment portion 77 and the base end of the bladebody 54. The sealing member 135 is provided on the rear end face of theblade attachment portion 77 to prevent toner from leaking from theportion between the rear end face of the blade attachment portion 77 andthe attachment member 134.

The attachment member 134 includes a front supporting member 138 shapedlike a plate, a back supporting member 136 of a substantially “L” shapein a sectional view, and screws 137. The front supporting member 138 isdisposed on the rear side of the sealing member 135. The base end of theblade body 54 is disposed on the rear side of the front supportingmember 138. The back supporting member 136 is disposed on the rear sideof the base end of the blade body 54. The screws 137 pass through theback supporting member 136, the base end of the blade body 54, and thefront supporting member 138 in the front-rear direction, to integrallysecure the back supporting member 136, the base end of the blade body54, and the front supporting member 138. With fixing screws 139, thebase end of the blade body 54 is fixed to the blade attachment portion77 while the base end of the blade body 54 and the attachment member 134sandwich the sealing member 135 between the base end of the blade body54 and the blade attachment portion 77.

As shown in FIGS. 4 and 5, the rear opening portion 73 is defined by theback supporting member 136 of the attachment member 134, the rear endsof the left and right sidewalls 69L, 69R, and the rear end of the rearbottom wall 76. The rear opening portion 73 is of a substantiallyrectangular shape extending in the first direction. A part of thedeveloping roller 38 is exposed from the rear opening portion 73. Morespecifically, as shown in FIG. 13, a part of the developing roller 38protrudes, in side view, from the inside to the outside of thedeveloping frame 36, through the rear opening portion 73.

As shown in FIG. 9, the developing roller 38 is provided such that eachend of the developing roller shaft 52 is rotatably supported in theopposing sidewalls 69L, 69R. A collar member 116 is mounted on an end ofthe developing roller shaft 52 extending from the left sidewall 69L. Asshown in FIGS. 5 and 7, the end of the developing roller shaft 52 isinserted, together with the collar member 116, into a developing rollershaft inserting portion 111 of a gear cover 93 (described below), whichis disposed on the side of the left sidewall 69L. The end of thedeveloping roller shaft 52 is rotatably supported in the developingroller shaft inserting portion 111 of the gear cover 93.

As shown in FIGS. 6 and 8 and described in detail below, a bearingmember 201, which is provided on the side of the right sidewall 69R, isfitted over the other end of the developing roller shaft 52 extendingfrom the right sidewall 69R. The other end of the developing rollershaft 52 extends through the bearing member 201. An electrode member 117is disposed on the side of the bearing member 201. A developing rollershaft covering portion 118 that is formed in the electrode member 117 isfitted over the other end of the developing roller shaft 52 passingthrough the bearing member 201. The developing roller shaft 52 isrotatably supported in the developing roller shaft covering portion 118of the electrode member 117. Thus, the ends of the developing roller 38is supported by the developing roller shaft inserting portion 111 of thegear cover 93, as well as the developing roller shaft covering portion118 of the electrode member 117.

When the developing cartridge 30 is installed in the developingcartridge installation portion 147, the collar member 116 and thedeveloping roller shaft covering portion 118 are guided by the guidegrooves 153, as shown in FIG. 17, formed in the sidewalls 144L, 144R ofthe developing cartridge installation portion 147. Thus, smoothinstallation of the developing cartridge 30 into the developingcartridge installation portion 147 can be ensured.

As shown in FIGS. 5 and 9, a rear side-end wall 78 is disposed below therear opening portion 73 on the rear end of the rear bottom wall 76 atits right and left sides with respect to the width direction of thedeveloping cartridge 30. Each rear side-end wall 78 is formed into asubstantially “L” shape with an inward lower portion thereof being cutout. A reinforcing portion 80 is disposed between the rear side-endwalls 78 on the rear end of the rear bottom wall 76, which is disposedbelow the rear opening portion 73.

The reinforcing portion 80 extends, along the width direction of thedeveloping cartridge 30, between the rear side-end walls 78. Thereinforcing portion 80 fits in the cutout portions of the rear side-endwalls 78. As shown in FIGS. 4 and 5, the reinforcing portion 80 isformed continuously from the rear end of the rear bottom wall 76. Thereinforcing portion 80 includes a reinforcing upper wall 82, areinforcing front wall 85, a reinforcing bottom wall 83, and reinforcingsidewalls 84. Those walls 82-85 are integrally formed into asubstantially box shape that is open rearward. More specifically, in asectional side view when taken along a direction perpendicular to thewidth direction of the developing cartridge 30, the reinforcing portion80 is formed into a substantially “U” shape with a rear portion beingopen.

The reinforcing upper wall 82 is integrally formed with the rear end ofthe rear bottom wall 76, to extend rearward. The reinforcing front wall85 is integrally formed with the rear end of the rear bottom wall 76, toextend downward from the front end of the reinforcing upper wall 82. Thereinforcing bottom wall 83 is disposed to face the reinforcing upperwall 82 in the vertical direction. The reinforcing bottom wall 83 isintegrally formed with the lower end of the reinforcing front wall 85 toextend rearward and downward.

The reinforcing sidewalls 84 are integrally formed with the ends of thereinforcing upper wall 82, the reinforcing front wall 85, and thereinforcing bottom wall 83, with respect to the width direction of thedeveloping cartridge 30. As shown in FIG. 4, a lower film 87 is attachedto the reinforcing upper wall 82. The lower film 87 is formed of, forexample, polyethylene terephthalate. The rear end of the lower film 87is attached to the upper surface of the reinforcing upper wall 82,extending frontward and upward to contact the lower surface of therubber roller 53 of the developing roller 38. Accordingly, the lowerfilm 87 closes a gap between the reinforcing upper wall 82 and thedeveloping roller 38, to prevent toner from leaking from the gap.

As show in FIGS. 4 and 7, guide plates 81 are provided on the bottomwall 71 of the developing frame 36 continuously from the reinforcingportion 80. The guide plates 81 are formed into a rib or flat plateshape extending in the front-rear direction, as well as downward fromthe bottom wall 71. The adjacent guide plates 81 are provided parallelto each other with some distance therebetween in the width direction ofthe developing cartridge 30.

More specifically, the rear end of each guide plate 81 is connected tothe reinforcing front wall 85 and the reinforcing bottom wall 83. Thefront end of each guide plate 81 is connected to the rear end portion ofthe front bottom wall 74. Each guide plate 81 extends downward from therear bottom wall 76, the central bottom wall 75 and the front bottomwall 74. Each guide plate 81 is integrally formed with the reinforcingbottom wall 83, the reinforcing front wall 85, the rear bottom wall 76,the central bottom wall 75, and the front bottom wall 74. The lower endof each guide plate 81 extends in a substantially straight manner towardthe front side from the rear end of the reinforcing bottom wall 83, andcurves upward and frontward below the central bottom wall 75, reachingthe rear end portion of the front bottom wall 74.

As show in FIGS. 7 and 12, a guide reinforcing plate 86 for reinforcingeach guide plate 81 is provided on the central bottom wall 75. The guidereinforcing plate 86 is of a plate shape extending downward from thecentral bottom wall 75 at some middle portion of the guide plates 81with respect to its front-rear direction, along a directionsubstantially perpendicular to the front-rear direction. The guidereinforcing plate 86 connects the guide plates 81 in the width directionof the developing cartridge 30 to reinforce each guide plate 81.

The front bottom wall 74 is provided with installation portions 133 andinstallation plates 88 for installing the developing cartridge 30 in thedeveloping cartridge installation portion 147 of the drum frame 58. Eachinstallation portion 133 is disposed on the middle portion, with respectto the front-rear direction, of the front bottom wall 74 at its eachend, with respect to the width direction of the developing cartridge 30.Each installation portion 133 is formed on the bottom of the frontbottom wall 74 into a substantially rectangular plate shape in a bottomview.

A pair of installation plates 88, which face each other in the widthdirection of the developing cartridge 30, is formed on the front ends ofthe front bottom wall 74 at each end, with respect to the widthdirection of the developing cartridge 30. Each installation plate 88 isformed into a substantially triangular shape extending downward from thefront bottom wall 74. The lower end of each installation plate 88extends in the front-rear direction slightly above each installationportion 133.

As shown in FIGS. 7 and 10, the front wall 72 of the developing frame 36is provided with a grip portion 89. The grip portion 89 is formed into asubstantially “U” shape in plane view. The handle 89 includes two handlesupporting plates 90 disposed on the front wall 72 with some distancetherebetween in the width direction of the developing cartridge 30 and ahandle 91 disposed between the handle supporting plates 90. Each handlesupporting plate 90 is of a plate shape extending forwardly from theupper portion of the front wall 72. The handle 91 is connected to thefront ends of the handle supporting plates 90.

A boss 132, as a pressed portion, is provided on each left and rightsidewall 69L, 69R of the developing frame 36. When the developingcartridge 30 is installed in the developing cartridge installationportion 147 of the drum frame 58, the bosses 132 contact the relevantpressing levers 150. Each boss 132 is provided at a front lower portionof each left and right sidewall 69L, 69R, so as to protrude outward fromthe outer surface of the sidewall 69L, 69R. As shown in FIGS. 14 and 15,each boss 132 is formed into a substantially “U” shape in side view thatis open rearward. Each boss 132 is disposed on the left and rightsidewall 69L, 69R at positions symmetric with respect to the firstdirection.

When the developing cartridge 30 is installed in the developingcartridge installation portion 147 of the drum frame 58, theinstallation portions 133 are placed on the relevant installation bases155, as shown in FIG. 2 and the installation plates 88 are placed on thebottom wall 143 of the developing cartridge installation portion 147.

As shown in FIGS. 8, 16, and 17, the front end of each boss 132 contactsthe relevant pressing lever 150. By the urging force of the compressionspring that urges the pressing lever 150, each boss 132 is pressedrearward by the relevant pressing lever 150. Accordingly, the developingframe 36 moves rearward relative to the developing cartridgeinstallation portion 147, so that the rubber roller 53 of the developingroller 38 is pressed against the photoconductive drum 28.

As shown in FIGS. 6 and 8, an engagement portion 181 is disposedintegrally with the right sidewall 69R behind the boss 132 so as toextend outward. When the developing cartridge 30 is installed in thedeveloping cartridge installation portion 147 of the drum cartridge 27,the engagement portion 181 is positioned below the lock lever 151. Thelock lever 151 engages with the engagement portion 181 with the urgingforce of the flexible portion 152. When the developing cartridge 30 isremoved from the developing cartridge installation portion 147, the locklever 151 is pressed down to disengage the engagement portion 181 fromthe lock lever 151.

(2) Gear Mechanism Portion and Gear Cover

As shown in FIG. 14, ends of the agitator rotating shaft 46, the supplyroller shaft 50, and the developing roller shaft 52 protrude outward inthe first direction from the left sidewall 69L, as a second sidewall.Disposed on the left sidewall 69L are a gear mechanism portion 92 fordriving the agitator rotating shaft 46, the supply roller shaft 50, andthe developing roller shaft 52 to rotate, and a gear cover 93 thatcovers the gear mechanism portion 92 as shown in FIGS. 5 and 13.

As shown in FIG. 14, the gear mechanism portion 92 is disposed on theleft sidewall 69L. The gear mechanism portion 92 includes an input gear94, as a driven coupling, a supply roller drive gear 95, as a supplyroller gear, a developing roller drive gear 115, as a developing rollergear, an intermediate gear 96, an agitator drive gear 97 and a detectiongear 98.

The input gear 94 is rotatably supported between the developing rollershaft 52 and the agitator rotating shaft 46 by an input gear supportingshaft 99 that extends outward from the left sidewall 69L in the firstdirection.

The input gear 94 is integrally provided with a driven coupling part100, as a first cylindrical portion, and a drive gear 101, as a secondcylindrical portion, that is concentrically disposed with the drivencoupling part 100 around the driven coupling part 100. The drivencoupling part 100 is of a hollow cylindrical shape. Engagement stopperportions 102, as driven parts, that engage with a drive coupling part200 (in FIG. 5), as a drive coupling, extend radially inward from theinner peripheral surface of the driven coupling part 100. The engagementstopper portions 102 are disposed opposite to each other with respect tothe input gear supporting shaft 99. Thus, the driven coupling part 100is formed as gear teeth that engage with the drive coupling part 200 (inFIG. 5).

The drive gear 101 is placed adjacent to the driven coupling part 100 inthe first direction between the driven coupling part 100 and the leftsidewall 69L.

The supply roller drive gear 95 is mounted on an end of the supplyroller shaft 50 to engage with the input gear 94 below the input gear94. The supply roller drive gear 95 is provided to rotate together withthe supply roller shaft 50, so that the supply roller drive gear 95 doesnot rotate relative to the supply roller shaft 50.

The developing roller drive gear 115 is mounted on an end of thedeveloping roller shaft 52 to engage with the input gear 94 on the lowerrear side of the input gear 94. The developing roller drive gear 115 isprovided to rotate together with the developing roller shaft 52, so thatthe developing roller drive gear 115 does not rotate relatively to thedeveloping roller shaft 52.

The intermediate gear 96 is rotatably supported in front of the inputgear 94 on an intermediate gear supporting shaft 103 extending outwardin the first direction from the left sidewall 69L. The intermediate gear96 is integrally provided with an external gear 104 that engages withthe input gear 94 and an internal gear 105 that engages with theagitator drive gear 97. The internal gear 105 is disposed on the innerside of the external gear 104 with respect to the width direction of thedeveloping cartridge 30.

The agitator drive gear 97 is mounted on an end of the agitator rotatingshaft 46 to rotate together with the agitator rotating shaft 46, so thatthe agitator drive gear 97 does not rotate relative to the agitatorrotating shaft 46. The agitator drive gear 97 is positioned at the lowerfront side of the intermediate gear 96. The agitator drive gear 97 isintegrally provided with an internal gear 106 that engages with theinternal gear 105 of the intermediate gear 96 and an external gear 107that engages with the detection gear 98. The external gear 107 isdisposed on the outer side of the internal gear 106 in the widthdirection of the developing cartridge 30.

The detection gear 98 is rotatably supported by a detection gearsupporting shaft 108 that extends outward in the first direction fromthe left sidewall 69L at the upper front side of the agitator drive gear97. The detection gear 98 is a partly tooth missing gear. The detectiongear 98 is integrally formed with a usage determination projection 109that extends outwardly in the radial direction of the detection gearsupporting shaft 108. The detection gear 98 is urged by a coiled spring110 wound around the detection gear supporting shaft 108 to engage withthe external gear 107 of the agitator drive gear 97.

As shown in FIG. 13, the gear cover 93 is attached to the left sidewall69L of the developing cartridge 30 to cover the gear mechanism portion92 from its outside with respect to the width direction of thedeveloping cartridge 30. The gear cover 93 has a developing roller shaftinsertion hole 111 that the developing roller shaft 52 and the collarmember 116 are inserted into, and an input hole 112 that exposes thedriven coupling part 100 therethrough. In addition, the gear cover 93 isprovided with a detection gear covering portion 113 that covers thedetection gear 98 on the front side of the input hole 112.

The detection gear covering portion 113 extends outwardly in the firstdirection. The detection gear 98 fits into the extended portion of thedetection gear covering portion 113. A sector-shaped detection window114 is formed on the rear side of the detection gear covering portion113. The usage determination projection 109, which moves along thecircumferential direction of the detection gear 98 in accordance withthe rotation of the detection gear 98, is exposed from the detectionwindow 114.

When the process cartridge 20 having the developing cartridge 30 settherein is installed in the main body casing 2, the drive coupling part200 is inserted into the driven coupling part 100 of the input gear 94of the developing cartridge 30, as shown in FIG. 5, to which drive forcefrom a motor (not shown) provided in the main body casing 2 istransmitted. Thus, the driven coupling part 100 engages with the drivecoupling part 200.

The drive coupling part 200 is removably inserted into the drivencoupling part 100, in association with operations of opening/closing thefront cover 7 of the main body casing 2. More specifically, when thefront cover 7 is open, the drive coupling part 200 withdraws from thedriven coupling part 100, so that the process cartridge 20 can beremoved from the main body casing 2. When the process cartridge 20having the developing cartridge 30 set therein is installed in the mainbody casing 2 through the opening 6 and then the front cover 7 isclosed, the drive coupling part 200 advances toward and is inserted intothe driven coupling part 100.

When the drive force from the motor is input from the drive couplingpart 200 to the driven coupling part 100, the input gear 94 is rotated.Then, the supply roller drive gear 95, which is directly engaged withthe drive gear 101 of the input gear 94, is rotated. Accordingly, thesupply roller shaft 50 causes the supply roller 37 to rotate. Further,the developing roller drive gear 115, which is directly engaged with thedrive gear 101 of the input gear 94, is rotated. Accordingly, thedeveloping roller shaft 52 causes the supply roller 37 to rotate.

Further, the external gear 104 of the intermediate gear 96, which isengaged with the drive gear 101 of the input gear 94, is rotated. Theinternal gear 105 of the intermediate gear 96, which is integrallyformed with the external gear 104, is rotated. When the internal gear105 of the intermediate gear 96 is rotated, the internal gear 106 of theagitator drive gear 97, which is engaged with the internal gear 105 ofthe intermediate gear 96, is rotated. Accordingly, the agitator rotatingshaft 46 cause the agitator 45 to rotate.

When the internal gear 106 of the agitator drive gear 97 is rotated, theexternal gear 107 of the agitator drive gear 97 integrally formed withthe internal gear 106 is rotated. Then, the detection gear 98 engagedwith the external gear 107 of the agitator drive gear 97 rotates.

When the developing cartridge 30 is unused, the detection gear 98 isplaced in such a position as shown in FIG. 14, where the detection gear98 is urged by the coiled spring 110 to engage with the external gear107 of the agitator drive gear 97. Once the detection gear 98 isrotated, the tooth missing portion of the detection gear 98 faces theexternal gear 107 of the agitator drive gear 97, so that the detectiongear 98 does not engage with the external gear 107. Consequently, thedetection gear 98 will not be rotated again. The usage determinationprojection 109 of the unused developing cartridge 30 moves across thedetection window 114 only once in one direction. In the laser printer 1,the determination as to whether the installed developing cartridge 30 isused or unused is made by detecting whether the usage determinationprojection 109 has been moved, with a usage detection sensor (not shown)provided in the main body casing 2

(3) Electrode Member

As shown in FIGS. 6, 8 and 15, the bearing member 201 that supports anend of the developing roller shaft 52 is provided on the right sidewall69R as a first sidewall. The bearing member 201 is formed ofnon-conductive resin material into a flat plate shape. A collar portion202, which has an inside diameter substantially same as the diameter ofthe developing roller shaft 52, is integrally formed on the bearingmember 201 at its rear end. The collar portion 202 is formed into acylindrical shape and inserts therein the developing roller shaft 52.The end of the developing roller shaft 52 is slidably and rotatablysupported on the inner peripheral surface of the collar portion 202.

Two engagement openings 128 are formed on the rear side of the bearingmember 201, so as to interpose the collar portion 202 between theengagement openings 128 in the vertical direction. An opening (notshown) for receiving the supply roller shaft 50 is formed on the frontside of the bearing member 201. Two engagement projections 129 areformed on the right sidewall 69R at positions corresponding to theengagement openings 128. The bearing member 201 is attached to the rightsidewall 69R such that the rear end of the bearing member 201 becomesflush with the rear end of the right sidewall 69R. With the bearingmember 201 attached to the right sidewall 69R, the developing rollershaft 52 and the supply roller shaft 50 are inserted into the collarportion 202 and the opening (not shown), respectively, and theengagement projections 129 are fitted into the relevant the engagementopenings 128.

The electrode member 117 as an electrode for applying the developingbias to the developing roller shaft 52 is formed on the surface of thebearing member 201. The electrode member 117 is formed of a conductiveresin including carbon powders. The electrode member 117 is providedintegrally with an attachment plate 120, the developing roller shaftcovering portion 118, as a developing roller shaft supporting portion,and a terminal portion 119.

The attachment plate 120 is formed of a thin plate into a substantiallytriangular shape in side view. The developing roller shaft coveringportion 118 is provided on the rear end of the attachment plate 120. Thedeveloping roller shaft covering portion 118 is formed into acylindrical shape to receive an end of the developing roller shaft 52and is disposed concentrically with the collar portion 202. Thedeveloping roller shaft covering portion 118 extends in the firstdirection from the rear end of the attachment plate 120.

The developing roller shaft 52 has a large diameter portion, which issupported by the collar portion 202, and a small diameter portion, whichis supported by the developing roller shaft covering portion 118. Thediameter of the large diameter portion is greater than that of the smalldiameter portion. The outside diameter of the developing roller shaftcovering portion 118 is substantially the same as the inside diameter ofthe collar portion 202. When the developing roller shaft coveringportion 118 is inserted over the developing roller shaft 52, a part ofthe developing roller shaft covering portion 118 is fitted into thecollar portion 202.

The terminal portion 119 is provided on the front end of the attachmentplate 120 with some distance between the terminal portion 119 and thedeveloping roller shaft covering portion 118 in the front-reardirection. The terminal portion 119 is provided with a base 121, acontact plate 122, as a contact portion.

The base 121 is provided integrally with a base plate 123 that extendsin the vertical direction to form a substantially elliptical shape inside view, and a loop-shaped outer rim plate 124 that extends outward inthe width direction of the developing cartridge 30 from the outerperiphery of the base plate 123. A part of the outer rim plate 124formed on the upper end of the base plate 123, extends outward in thefirst direction longer than the remaining part of the outer rim plate124.

The contact plate 122 is of a substantially “U” shape in side view thatis open downward. The contact plate 122 extends outward in the firstdirection from the outer rim plate 124 formed on the upper end of thebase 121.

The attachment plate 120 is formed with an upper reinforcing rib 125, alower reinforcing rib 126, and a supply roller shaft covering portion127, as a supply roller supporting portion. The upper reinforcing rib125 extends outward in the first direction from the attachment plate120. The upper reinforcing rib 125 is formed such that it extendsrearward and downward toward the developing roller shaft coveringportion 118 from the rear end of the contact plate 122 and is connectedto the developing roller shaft covering portion 118.

The lower reinforcing rib 126 extends outward in the first directionfrom the attachment plate 120 to form a substantially upward-open “U”shape in side view while covering the lower part of the terminal portion119. More specifically, the lower reinforcing rib 126 includes a firstlower reinforcing rib 126A, a second lower reinforcing rib 126B, and athird lower reinforcing rib 126C that are continuously formed.

The first lower reinforcing rib 126A extends rearward and downward fromits upper end. The upper end of the first lower reinforcing rib 126A isconnected to the upper reinforcing rib 125 provided between thedeveloping roller shaft covering portion 118 and the terminal portion119. The lower end of the first lower reinforcing rib 126A is connectedto the third lower reinforcing rib 126C.

The upper end of the second lower reinforcing rib 126B is connected tothe front lower end of the base 121. The upper end of the second lowerreinforcing rib 126B extends rearward and downward parallel to the firstlower reinforcing rib 126A. The lower end of the second lowerreinforcing rib 126B is connected to the third lower reinforcing rib126C.

The third lower reinforcing rib 126C is disposed below the base 121 soas to connect the lower ends of the first lower reinforcing rib 126A andthe second lower reinforcing rib 126B.

The supply roller shaft covering portion 127 is disposed between thebase 121 and the third lower reinforcing rib 126C. The supply rollershaft covering portion 127 is formed into a cylindrical shape to receivean end of the supply roller shaft 50. The supply roller shaft coveringportion 127 extends outward in the first direction from the attachmentplate 120 shorter than the outer rim plate 124.

A screw hole (not shown) is formed on the base plate 123 of the base121. A screw hole (not shown) is formed on the bearing member 201 at aposition corresponding to the screw hole on the base plate 123. Athreaded hole (not shown) is formed on the right sidewall 69R at aposition corresponding to the screw hole on the base plate 123.

The electrode member 117 is attached to the right sidewall 69R, whileinserting ends of the developing roller shaft 52 and the supply rollershaft 50 into the developing roller shaft covering portion 118 and thesupply roller shaft covering portion 127, respectively, using a screw130 that is inserted into the screw hole on the base plate 123 andscrewed into the threaded hole of the right sidewall 69R, through thescrew hole on the bearing member 201.

With such a structure, the end of the developing roller shaft 52slidably contacts the inner peripheral surface of the developing rollershaft covering portion 118. Similarly, the end of the supply rollersupply shaft 50 slidably contacts the inner peripheral surface of thesupply roller shaft covering portion 127.

When the process cartridge 20 having the developing cartridge 30 settherein is installed in the main body casing 2, a developing biasterminal 131, as a feeding member, provided in the main body casing 2,elastically contacts the upper surface of the contact plate 122, asshown in FIG. 15 by the imaginary line.

More specifically, the contact plate 122 is disposed near the supplyroller shaft 50 inserted into the supply roller shaft covering portion127 with respect to the vertical direction. The developing bias terminal131 elastically contacts the contact plate 122 on its surface oppositeto the surface facing the supply roller supply shaft 50.

The developing bias terminal 131 is connected to a high-voltage circuitboard (not shown) that is provided in the main body casing 2 to applythe developing bias. When the developing bias terminal 131 elasticallycontacts the upper surface of the contact plate 122, the developing biasfrom the high-voltage circuit board is applied to the developing rollershaft 52, via the electrode member 117 formed of conductive resin. Then,the developing bias is applied to the conductive rubber roller 53 fromthe developing roller shaft 52.

The electrode member 117 supports both the developing roller shaft 52and the supply roller shaft 50, so that the same bias as the developingbias is applied to the conductive sponge roller 51, via the supplyroller shaft 50.

(4) Relative Positions of Input Gear and Electrode Member

In the developing cartridge 30, the contact plate 122 of the electrodemember 117 is disposed within a plane of projection when the input gear94 is projected in a direction parallel to the developing roller shaft52, that is in the first direction, as shown in FIGS. 11, 13, and 15.

More specifically, as shown in FIGS. 19 and 20, the contact plate 122 ofthe electrode member 117 is disposed within a plane of projection whenthe driven coupling part 100 of the input gear 94 is projected in thefirst direction. Further, the contact plate 122 is disposed to contactthe developing bias terminal 131 in a plane of projection when thedriven coupling part 100 is projected in the first direction.Especially, the contact plate 122 is disposed to contact the developingbias terminal 131 on the extension line (a second axis line X2 as willbe described below) of the input gear supporting shaft 99 on which thedriven coupling part 100 rotates.

As shown in FIG. 11, a first axis line X1, which is an axis of thedeveloping roller shaft 52, and the second axis line X2 which is an axisof the input gear 94 are disposed in parallel and equidistantly in thefront-rear direction. A part of the contact plate 122 of the electrodemember 117 is disposed on the second axis line X2. More specifically, asshown in FIG. 13, a first line L1 connects, in a direction perpendicularto the axial direction of the developing roller shaft 52, an axis of theinput gear supporting shaft 99, on which the input gear 94 rotates, andan axis of the developing roller shaft 52, on which the developingroller 38 rotates. As shown in FIG. 15, a second line L2 connects, in adirection perpendicular to the axial direction of the developing rollershaft 52, a contact point of the contact plate 122 to the developingbias terminal 131, which is a part of the contact plate 122 of theelectrode member 117, and the axis of the developing roller shaft 52, onwhich the developing roller 38 rotates. As shown in FIG. 11, the firstline L1 and the second line L2 are parallel to each other. A firstdistance D1 between the first axis line X1 and the second axis line X2on the first line L1, as shown in FIG. 13, and a second distance D2between the first axis line X1 and the second axis line X2 on the secondline L2, as shown in FIG. 15, are equal.

(5) Effects of Developing Cartridge

In the above-structured developing cartridge 30, the contact plate 122of the electrode member 117 is disposed within a plane of projectionwhen the input gear 94 is projected in a direction parallel to thedeveloping roller shaft 52, which is in the first direction. Morespecifically, the contact plate 122 of the electrode member 117 isdisposed in a plane of projection when the driven coupling part 100 isprojected in the first direction. In some aspects, the contact plate 122contacts the developing bias terminal 131 within a plane of projectionwhen the driven coupling part 100 is projected in the first direction.Especially, the contact plate 122 contacts the developing bias terminal131 on the extension line of the input gear supporting shaft 99 on whichthe driven coupling part 100 rotates. Further, the first axis line X1and the second axis line X2 are parallel to each other. A part of thecontact plate 122 of the electrode member 117 is disposed on the secondaxis line X2. More specifically, the first line L1 and the second firstline L2 are parallel to each other and the first distance D1 and thesecond distance D2 are equal.

Therefore, even when such rotation or torsion power is exerted on thedeveloping cartridge 30 that produces rotation or torsion of thedeveloping cartridge 30 about the input gear 94 when the drive forcefrom the motor is input to the driven coupling part 100 from the drivecoupling part 200, significant influences of the rotation or torsionpower on the contact plate 122 of the electrode member 117 can beprevented. Consequently, the contact plate 122 is prevented from beingplaced out of position. Thus, the contact plate 122 and the developingbias terminal 131 stably contact each other, so that power can be stablysupplied to the developing roller shaft 52 from the electrode member117.

If the contact point between the contact plate 122 and the developingbias terminal 131 is placed at any position within a plane of projectionwhen the driven coupling part 100 is projected in the first direction,influences by the rotation or torsion power can be minimized

Further, in the developing cartridge 30, each end of the developingroller 38 is supported in the left or right sidewalls 69L, 69R byrotatably supporting each end of the developing roller shaft 52 in theleft or right sidewalls 69L, 69R. Accordingly, while the developingroller 38 is securely supported, the developing bias can be stablyapplied to the rubber roller 53.

One end of the developing roller shaft 52 is rotatably supported in thedeveloping roller shaft inserting portion 111 of the gear cover 93, viathe collar member 116. The other end of the developing roller shaft 52is rotatably supported in the developing roller shaft covering portion118 of the electrode member 117. Each end of the developing roller 38 isalso supported by the developing roller shaft inserting portion 111 ofthe gear cover 93 or the developing roller shaft covering portion 118 ofthe electrode member 117. Thus, the developing roller 38 can be securelysupported while the developing roller shaft 52 is efficiently insertedinto the developing roller shaft inserting portion 111 of the gear cover93 and the developing roller shaft covering portion 118 of the electrodemember 117. Therefore, the developing bias can be stably applied to therubber roller 53.

In the developing cartridge 30, the electrode member 117 is formed ofconductive resin. Therefore, the electrode member 117 can be formed intoany shape to stably apply the developing bias to the rubber roller 53.

When the process cartridge 20 having the developing cartridge 30 settherein is installed in the main body casing 2, the developing biasterminal 131 elastically contacts the upper surface of the contact plate122. The developing bias is applied from the developing bias terminal131 to the developing roller shaft 52 by the high-voltage circuit board,via the electrode member 117. Then, the developing bias is applied fromthe developing roller shaft 52 to the conductive rubber roller 53. Thus,the developing bias can be reliably applied from the electrode member117 to the rubber roller 53.

The developing roller shaft 52 is formed of metal, so that thedeveloping bias can be further reliably applied from the electrodemember 117 to the rubber roller 53. In addition, in the developingcartridge 30, the developing roller shaft covering portion 118 of theelectrode member 117 rotatably supports the developing roller shaft 52.Therefore, it is not necessary to support the developing roller shaft 52with another member or components. Thus, reduction of the number ofcomponents and costs can be achieved.

In the developing cartridge 30, the input gear 94 is provided integrallywith the driven coupling part 100 and the drive gear 101. Therefore,while the driven coupling part 100 can reliably receive the drive forcefrom the drive coupling part 200, the drive gear 101 conveys the driveforce to the supply roller drive gear 95, the developing roller drivegear 115, and the intermediate gear 96. Thus, the supply roller shaft 50and the developing roller shaft 52, as well as the agitator rotatingshaft 46 can be reliably rotated.

The driven coupling part 100 is of a hollow cylindrical shape. Thedriven coupling part 100 is formed as gear teeth with the engagementstopper portions 102 extending radially inward from the inner peripheralsurface of the driven coupling part 100. Therefore, as the engagementstopper portions 102 are engaged with the drive coupling part 200, thedrive force can be reliably received from the drive coupling part 200.

As the drive gear 101 of the input gear 94 is engaged directly with thedeveloping roller drive gear 115, the drive force, which is input fromthe drive coupling part 200 to the input gear 94, is directlytransmitted to the developing roller drive gear 115 from the input gear94. Therefore, the developing roller 38 can be reliably rotated.Further, as the drive force is thus transmitted, drive force from themain body casing 2 is not directly transmitted to the developing rollerdrive gear 115, so that the developing roller shaft 52 can be used as aguide. More specifically, when the developing cartridge 30 is installedin the developing cartridge installation portion 147, the collar member116 and the developing roller shaft covering portion 118 provided on thedeveloping roller shaft 52 are guided along the guide grooves 153. Thus,the developing roller shaft 52 can be used as a guide. Consequently, aguide does not have to be additionally provided, and the number ofcomponents to be used and costs can be reduced.

The drive gear 101 of the input gear 94 also engages directly with thesupply roller drive gear 95, so that the drive force input from thedrive coupling part 200 to the input gear 94 is transmitted directly tothe supply roller drive gear 95. Therefore, the supply roller 37 can bereliably rotated. Further, as the drive force is thus transmitted, thedrive force is directly transmitted from the input gear 94 to thedeveloping roller drive gear 115 and the supply roller drive gear 95.Thus, the drive force can be transmitted effectively, and the developingroller 38 and the supply roller 37 can be effectively rotated.

The electrode member 117 is provided with the developing roller shaftcovering portion 118 and the supply roller shaft covering portion 127.Accordingly, the developing roller shaft 52 and the supply roller shaft50 can be reliably supported by the developing roller shaft coveringportion 118 and the supply roller shaft covering portion 127,respectively.

When the developing cartridge 30 is installed in the main body casing 2,the developing bias terminal 131 elastically contacts the upper surfaceof the contact plate 122, which is positioned above the developingroller shaft covering portion 118 and the supply roller shaft coveringportion 127 and is opposite to the surface facing the supply rollershaft 50. Therefore, reliable contact between the developing biasterminal 131 and the contact plate 121 can be achieved. Thus, thedeveloping bias can be reliably applied by the high-voltage circuitboard (not shown) to the contact plate 122, via the developing biasterminal 131.

When the developing cartridge 30 is installed in the developingcartridge installation portion 147 of the drum frame 58, the front endsof the bosses 132 contact the relevant pressing levers 150. By theurging force of the compression springs that urge the pressing levers150, each boss 132 is pressed rearward by the relevant pressing lever150. Thus, the developing roller 38 is pressed against thephotoconductive drum 28. With the reliable contact between thedeveloping roller 38 and the photoconductive drum 28, the electrostaticlatent image formed on the photoconductive drum 28 can be reliablydeveloped by the toner carried on the developing roller 38.

Each boss 132 extends outwardly in the first direction from the outersurface of each left and right sidewall 69L, 69R at a front lower sideof each sidewall 69L, 69R. With such a structure, the bosses 132 canreliably contact the relevant pressing levers 150, so that reliablecontact between the developing roller 38 and the photoconductive drum 28can be ensured.

The developing cartridge 30 is removably installed in the drum cartridge27. The developing cartridge 30 can be replaced with a new one inaccordance with the residual amount of the toner, regardless of the lifeof the photoconductive drum 28. The drum cartridge 27 can be replaced inaccordance with the life of the photoconductive drum 28, regardless ofthe residual amount of the toner contained in the developing cartridge30.

3. Other Aspects

(1) Electrode Member According to Other Aspects

In the above description, the electrode member 117, as an electrode,including the attachment plate 120, the developing roller shaft coveringportion 118, and the terminal portion 119, is integrally formed ofconductive resin, as shown in FIGS. 6, 8 and 15. However, the attachmentplate 120, the developing roller shaft covering portion 118, and theterminal portion 119 may be separately formed and then assembledtogether into the electrode member 117.

For example, the terminal portion 119 provided with the base 121 and thecontact plate 122 may be integrally formed of metal, as an electrode.The attachment plate 120 and the developing roller shaft coveringportion 118 may be integrally formed of conductive resin, as aconductive member. Then, the terminal portion 119 may be secured to theattachment plate 120 using the screw 130. Thus, the electrode member 117may be formed.

With such electrode member 117, the developing bias can be reliablyapplied to the contact plate 122 from the developing bias terminal 131because the terminal portion 119 is formed of metal. Power can bereliably supplied to the developing shaft 52, via the attachment plate120 and the developing roller shaft covering portion 118, from theterminal portion 119, which is a part of the electrode member 117.

The terminal portion 119 indirectly contacts the developing shaft 52,via the attachment plate 120 and the developing roller shaft coveringportion 118. Therefore, the position of the terminal portion 119relative to the developing roller shaft 52 or the position of thedeveloping roller shaft 52 relative to the terminal portion 119 can beselected freely. Thus, while improving the design efficiency, power canbe reliably supplied from the contact plate 122 to the developing rollershaft 52.

(2) Developing Roller Shaft According to Other Aspects

In the above description, the developing roller shaft 52 is formed ofmetal. However, the developing roller shaft 52 may be formed ofconductive resin. Further, the developing roller shaft 52 may be formedof an insulating material, such as an insulating resin material.

When the developing roller shaft 52 is formed of an insulating material,the electrode member 117 and the rubber roller 53 may be electricallyconnected and the developing bias may be directly applied from theelectrode member 117 to the rubber roller 53. In this case, theresistance of the rubber roller 53 may be set lower than that of therubber roller 53 according to the above-described aspects.

For example, as shown in FIG. 18, the surface of an insulatingdeveloping roller shaft 52A, may be covered with a conductive sheet 154formed of metal foil, such as an aluminum foil, so as to contact therubber roller 53. The conductive sheet 154 may contact the innerperipheral surface of the developing roller shaft covering portion 118.With such a structure, the developing bias may be applied from theelectrode member 117 to the rubber roller 53, via the conductive sheet154.

(3) Input Gear According to Other Aspects

In the above description, the input gear 94 is integrally formed withthe driven coupling part 100 and the drive gear 101. However, the inputgear 94 may be integrally formed with, for example, the drive gear 101and the engagement stopper portions 102.

FIG. 21 is a perspective view of the developing cartridge, correspondingto FIG. 6, with an electrode member detached from the developingcartridge. FIG. 22 is a perspective view of the developing cartridge,corresponding to FIG. 8, with the electrode member detached from thedeveloping cartridge. FIG. 23 is a right side view of the developingcartridge, corresponding to FIG. 15. FIG. 24 is a sectional view of thedeveloping cartridge taken along line A-A of FIG. 23. FIG. 25 is asectional view of the developing cartridge taken along line B-B of FIG.23.

With reference to FIGS. 21 to 25, the developing cartridge according tosome further aspects will be described in detail below. It is to benoted that the similar reference numerals designate similar components,and a detailed explanation thereof is omitted.

(1) Developing Frame

The developing cartridge 30 according to some aspects has the developingframe 36 similar to that of the developing cartridge 30 according toabove-described aspects, except for the following structures.

As shown in FIGS. 21 and 22, the developing frame 36 according to someaspects has a cylindrical screw portion 79, as a screw portion, forattaching the electrode member 117 to the right sidewall 69R closing theside (right side) of the developing chamber 42. The cylindrical screwportion 79 is of a cylindrical shape extending outward from the rightsidewall 69R. Threaded grooves are formed on the inner circumferentialsurface of the cylindrical screw portion 79 for screwing a shaft 130 aof the screw 130 into the cylindrical screw portion 79. Upper and lowerends of a free end 79 a of the cylindrical screw portion 79 are cut outalong the front-rear direction. Thus, the free end 79 a is ofsubstantially oval shape having flat portions on the upper and lower endthereof extending in the front-rear direction.

(2) Gear Mechanism Portion and Gear Cover

The developing cartridge 30 according to some aspects has the gearmechanism portion 92 and the gear cover 93 similar to those of thedeveloping cartridge 30 according to earlier described aspects.

(3) Electrode Member

The developing cartridge 30 according to some aspects has the electrodemember 117 similar to that of the developing cartridge 30 according toearlier described aspects, except for the following structures.

An opening 161 is formed on the front side of the bearing member 201.When the bearing member 201 is attached to the right sidewall 69R, thedeveloping roller shaft 52 is inserted into the collar portion 202 andthe supply roller shaft 50 is inserted into the opening 161. To preventthe cylindrical screw portion 79, which extends outward from the rightsidewall 69R in the first direction from interfering with the bearingmember 201, a part of the outer periphery of the bearing member 201where the cylindrical screw portion 79 extends, is cut out. When thebearing member 201 is attached to the right sidewall 69R, thecylindrical screw portion 79 is exposed from the outer periphery of thebearing member 201.

The electrode member 117, as an electrode for applying developing biasto the developing roller shaft 52, is provided separately from thebearing member 201 on the right sidewall 69R, such that a part of thebearing member 201 is interposed between the right sidewall 69R and theelectrode member 117. As shown in FIG. 24, the base plate 123, as anattached portion, of the electrode member 117, is disposed parallel tothe attachment plate 120 at a position outward of the attachment plate120 with respect to the first direction. As shown FIGS. 21 and 22, ascrew hole 140, as an insertion portion, is formed at a substantiallycentral portion of the base plate 123. In association with the free end79 a of the cylindrical screw portion 79, the screw hole 140 is of asubstantially oval shape having flat portions that extend in thefront-rear direction.

The outer rim plate 124 extends in the first direction from the outerperiphery of the base plate 123 so as to connect the base plate 123 andthe attachment plate 120. In the developing cartridge 30 according tosome aspects, the electrode member 117 is attached to the right sidewall69R in the following manner. First, ends of the developing roller shaft52 and the supply roller shaft 50 are inserted into the developingroller shaft covering portion 118 and the supply roller shaft coveringportion 127, respectively. At the same time, the cylindrical screwportion 79 provided on the right sidewall 69R is inserted into the screwhole 140 on the base plate 123, to fit the free end 79 a of thecylindrical screw portion 79 in the screw hole 140. Thereafter, thescrew 130, as a fixing member, is screwed into the cylindrical screwportion 79 exposed from the base plate 123.

The screw 130 is integrally formed with the shaft 130 a having screwthreads formed along an axial direction thereof and a screw head 130 bprovided on an end of the shaft 130 a, as a separation prevention part,that extends, like a mushroom, in the radial direction of the shaft 130a. The diameter of the screw head 130 b is the same as or slightlylarger than the diameter of the cylindrical screw portion 79.

As shown in FIGS. 24 and 25, the screw 130 is screwed into thecylindrical screw portion 79, until an inward end face If, as a secondend face, of the screw head 130 b with respect to the axial direction ofthe screws 130 contacts a free end face Ff, as a third end face, of thecylindrical screw portion 79.

As the electrode member 117 is thus attached to the right sidewall 69R,the attachment plate 120 disposed between the developing roller shaftcovering portion 118 and the base 121 contacts the bearing member 201,so that the electrode member 117 is positioned with respect to the firstdirection (width direction of the developing cartridge 30). The free endface Ff of the cylindrical screw portion 79 is disposed to protrudeoutward in the first direction toward the side of the screw head 130 bslightly (e.g., 0.2 mm) from an outward face Of, as a first end face, ofthe base plate 123.

The inward end face If of the screw head 130 b with respect to the axialdirection of the screws 130 is disposed so as to contact the free endface Ff of the cylindrical screw portion 79 and to face the outward faceOf of the base plate 123 with a small distance (e.g., 0.2 mm) above andbelow the screw shaft 130 a. The screw head 130 b restricts or prevents,at a position opposite to the free end face Ff of the cylindrical screwportion 79, the separation or removal of the base plate 123 from thecylindrical screw portion 79.

Due to the distance between the inward end face If of the screw head 130b and the outward face of the base plate 123, the electrode member 117does not make intimate contact with the outward face Of of the baseplate 123. Accordingly, the electrode member 117 can move slightly, inassociation with a small clearance between the electrode member 117 andthe cylindrical screw portion 79. When the developing bias terminal 131provided in the main body casing 2 elastically contacts the uppersurface of the contact plate 122, the developing roller shaft coveringportion 118 moves slightly within the range of the small clearancebetween the electrode member 117 and the cylindrical screw portion 79.Accordingly, the outer circumferential surface of the end of thedeveloping roller shaft 52 makes slidable and intimate contact with theinner circumferential surface of the developing roller shaft coveringportion 118. Thus, the end of the developing roller shaft 52 isrotatably supported by the developing roller shaft covering portion 118.The supply roller shaft covering portion 127 also moves within the rangeof the small clearance. Therefore, the outer circumferential surface ofthe end of the supply roller shaft 50 also makes slidable and intimatecontact with the inner circumferential surface of the supply rollershaft covering portion 127. Thus, the end of the supply roller shaft 50is rotatably supported by the supply roller shaft covering portion 127.

(4) Effects of Developing Cartridge

As described above, in the developing cartridge 30, the electrode member117 can move slightly within the range of the small clearance. When thedeveloping bias terminal 131 provided in the main body casing 2elastically contacts the upper surface of the contact plate 122, thedeveloping roller shaft covering portion 118 moves within the range ofthe small clearance. Accordingly, while the outer circumferentialsurface of the end of the developing roller shaft 52 reliably makescontact with the inner circumferential surface of the developing rollershaft covering portion 118, the developing roller shaft 52 is rotated.In other words, the developing roller shaft covering portion 118rotatably supports the developing roller shaft 52, and the electrodemember 117 is moved such that the developing roller shaft coveringportion 118 makes reliable contact with the developing roller 52 whenthe developing bias terminal 131 contacts the contact plates 122.Therefore, the developing bias is reliably applied from the developingbias terminal 131 to the developing shaft 52, via the contact plate 122and the developing roller shaft covering portion 118.

In the developing cartridge 30, the electrode member 117 is attached tothe right sidewall 69R readily using the screw 130, such that theelectrode member can move slightly by the small clearance.

More specifically, when the inward end face If of the screw head 130 bwith respect to the axial direction of the screws 130 contacts the freeend face Ff of the cylindrical screw portion 79, the screw head 130 band the base plate 123 are disposed with some distance therebetween.Thus, the distance between the outward face Of of the base plate 123 andthe inward end face If of the screw head 130 b can be provided preciselyand reliably. Consequently, the developing roller shaft covering portion118 can make reliable contact with the developing roller shaft 52 whileensuring smooth rotation of the developing roller shaft 52 relative tothe developing roller shaft covering portion 118.

In the developing cartridge 30, the developing roller shaft coveringportion 118 and the contact plate 122 are provided so as to extendoutward in the first direction from the right sidewall 69R along thedeveloping roller shaft 52. Therefore, while the contact plate 122reliably makes contact with the developing bias terminal 131, the smoothrotation of the developing roller shaft 52 relative to the developingroller shaft covering portion 118 can be ensured and the developingroller shaft covering portion 118 can reliably make contact with thedeveloping roller shaft 52.

In the developing cartridge 30, the supply roller shaft covering portion127 is provided in the electrode member 117. While the supply rollershaft 50 is rotatably supported by the supply roller shaft coveringportion 127, the developing bias can be applied to the supply rollershaft 50 as well.

In the developing cartridge 30, the bearing member 201 is provided onthe right sidewall 69R separately from the electrode member 117. As thebearing member 201 can bear or support the developing roller shaft 52,the developing roller shaft covering portion 118 can reliably makecontact with the developing roller shaft 52 while ensuring smoothrotation of the developing roller shaft 52. Even when a bearing cannotbe used as the electrode member 117, power can be reliably supplied tothe developing roller shaft 52.

(5) Electrode Member According to Other Aspects

In the above-described description, with the distance between the inwardend face If of the screw head 130 b and the outward face Of of the baseplate 123, the developing roller shaft covering portion 118 is movedsuch that its inner peripheral surface reliably contacts the outerperipheral surface of the end of the developing roller shaft 52.However, the developing roller shaft covering portion 118 may be movedby a different manner, such that its inner peripheral surface reliablycontacts the outer peripheral surface of the end of the developingroller shaft 52.

For example, before the electrode member 117 is attached to the rightsidewall 69R, the electrode member 117 may be formed such that distancebetween a center of the screw hole 140 of the electrode member 117 andan axis of the developing roller shaft covering portion 118 slightlydiffers from distance between an axis of the cylindrical screw portion79 and an axis of the developing roller shaft 52. As the thus-formedelectrode member 117 is attached to the right sidewall 69R, the centerof the screw hole 140 and the axis of the cylindrical screw portion 79match with each other. However, the axis of the developing roller shaftcovering portion 118 and the axis of the developing roller shaft 52slightly differs from each other and does not match. Therefore, theouter peripheral surface of the end of the developing roller shaft 52reliably contacts the inner peripheral surface of the developing rollershaft covering portion 118.

General Structure of Laser Printer

FIG. 26 shows a perspective view of a color laser printer 210, as animage forming apparatus, according to another aspect of the invention.It should be noted that like numerals are used for like correspondingparts, a detailed description thereof is omitted and the abovedescription may be applied.

Referring to FIG. 26, a main body casing 211 of the color laser printer210 is structured so as to allow a process cartridge 230 to be removablyinstalled therein. The process cartridge 230 according to this aspect isprovided with sets of developing cartridges 240 and drum units 250. Thedeveloping cartridges 240 are installed in the process cartridge 230,with a longitudinal direction of the developing cartridges 240 parallelto a width direction of the color laser printer 210, as indicated by thearrow W. The developing cartridges 240 and the drum units 250 arearranged in a front-rear direction L, along a longitudinal direction ofthe color laser printer 210.

A pair of slide guide frames 211 c is provided on inner wall surfaces ofthe main body casing 211. The slide guide frames 211 c are structured tosupport the process cartridge 230 in the main body casing 211 and toguide the installation/removal of the process cartridge 230 in/from themain body casing 211 along the front-rear direction L. The slide guideframes 211 c will be described in detail below.

A pair of linear cam mechanisms 219 is provided on the inner wallsurfaces of the walls of the main body casing 211. The linear cammechanisms 219 are structured to selectively press down the developingcartridges 240 arranged along the front-rear direction L. The linear cammechanisms 219 will be described in detail below.

The color laser printer 210 according to this aspect is structured toperform full-color printing using the developing cartridges 240containing toner of different colors, that is, using a black developingcartridge 240K, a cyan developing cartridge 240C, a magenta developingcartridge 240M, and a yellow developing cartridge 240Y. Toner images ofmultiple colors are attached and fused onto a recording medium (sheet).

(1) General Structure of Developing Cartridge

FIG. 27 is a front view of the developing cartridge 240 according to theillustrative aspect shown in FIG. 26. FIG. 28 is a perspective back viewof the developing cartridge 240 shown in FIG. 27. FIGS. 29 and 30 areperspective front views of the developing cartridge 240 shown in FIG.27.

Referring to FIG. 27, a developing roller 244 is disposed in adeveloping frame 241. The developing frame 241 is structured such that apart of a toner carrying peripheral surface 244 b of the developingroller 244 may be exposed outside from an opening portion 241 d formedon a lower part of the developing frame 241. A developing roller shaft244 a, which constitutes an axis of the developing roller 244, isrotatably supported by a pair of side walls 241 a of the developingframe 241.

(a) Structures of Conductive Member and Drive Force Input Portion

A collar member 246 is mounted on an end of the developing roller shaft244 a associated with one of the side walls 241 a (left side wall inFIG. 27). An electrode member 247 is provided on the one of the sidewalls 241 a on which the collar member 246 is provided. A gear mechanismportion 248 is disposed on the other side wall 241 a (right side wall inFIG. 27).

Referring to FIG. 28, the electrode member 247 includes an attachmentplate 247 a and a terminal portion 247 b. The attachment plate 247 a isformed of a substantially flat shape. The attachment plate 247 a hasholes into which a supply roller shaft 243 a and the developing rollershaft 244 a are inserted. The attachment plate 247 a is electricallyconnected to the supply roller shaft 243 a and the developing rollershaft 244 a by contacting thereto.

The terminal portion 247 b extends outward from the attachment plate247. An outer shape of the terminal portion 247 b is of a cylindricalshape. In other words, the outer shape of the terminal portion 247 b issubstantially ring shaped when viewed from a side along the longitudinaldirection of the developing cartridge 240. An outer peripheral surfaceof the terminal portion 247 b is formed as a smooth cylindrical surface,so that a feeding member, which is configured to feed power to theterminal portion 247 b by contacting the outer peripheral surface of theterminal portion 247 b, may smoothly slide on the outer peripheralsurface of the terminal portion 247 b.

Referring to FIG. 29, the gear mechanism portion 248 includes a couplingpart 248 a. The coupling part 248 a includes a driven coupling part 248a 1 and an input opening portion 248 a 2.

The driven coupling part 248 a 1 is structured to engage with a driverotor disposed on the main body casing 211 as shown in FIG. 26, toreceive drive force via the drive rotor. The input opening portion 248 a2 is formed of a cylindrical thin member so as to extend outward. Thedriven coupling part 248 a 1 is rotatably disposed in the input openingportion 248 a 2.

An outer shape of the driven coupling part 248 a 1 is formed so as tohave a larger outside diameter than that of the collar member 246 andthe terminal portion 247 b of the electrode member 247, when viewed froma side along the longitudinal direction of the developing cartridge 240.More specifically, the outside diameter of the driven coupling part 248a 1 is about one-and-a-half times larger than that of the terminalportion 247 b and a small diameter portion 246 a (in FIG. 38) of thecollar member 246 that engages with the drum unit 250 (as shown in FIG.26). The outer shape of the driven coupling part 248 a 1 is formed toinclude the outside diameter of the terminal portion 247 b when viewedalong the longitudinal direction of the developing roller shaft 244 a.More specifically, as will be described in detail below, inside theouter shape of the driven coupling part 248 a 1 is a feeding memberpressing position where the terminal portion 247 b and the feedingmember contact each other, when viewed along the longitudinal directionof the developing roller shaft 244 a.

(b) General Structure of Developing Frame

Referring back to FIG. 28, formed on an upper wall 241 c of thedeveloping frame 241 is a pair of separation bosses 241 f configured tourge the developing cartridge 240 upward when an image forming operationis not performed. The separation bosses 241 f extend outward along thelongitudinal direction of the developing cartridge 240 from front endsof the upper wall 241 c.

A holding portion 241 g is disposed on the upper wall 241 c of thedeveloping frame 241. The holding portion 241 g is pivotally supportedabout hinges 241 h disposed on front portions of the upper wall 241 c.For the installation and removal of the developing cartridge 240, theholding portion 241 g is pivotally moved to an upright position, asshown in FIG. 30, so that a user may hold the holding portion 241 g. Theholding portion 241 g is structured to urge the developing frame 241downward as the holding portion 241 g placed in a rest position, asshown in FIGS. 28 and 29, is pressed down during the image formingoperation.

Referring to FIG. 28, the holding portion 241 g is formed with a pair ofpressed bosses 241 g 1 for urging the developing frame 241 downwardduring the image forming operation. The pressed bosses 241 g 1 extendoutward along the longitudinal direction of the developing cartridge 240from free ends of the holding portion 241 g. Pressing portions 241 g 2are disposed inwardly of the pressed bosses 241 g 1 with respect to thelongitudinal direction of the developing cartridge 240. When the pressedbosses 241 g 1 are pressed down, the pressing portions 241 g 2 may beurged toward press actuation mechanisms 241 k disposed below thepressing portions 241 g 2.

A pair of the press actuation mechanisms 241 k is disposed on the upperwall 241 c of the developing frame 241. The press actuation mechanisms241 k are disposed at ends of the upper wall 241 c with respect to itslongitudinal direction, in association with a pair of the pressingportions 241 g 2. The press actuation mechanisms 241 k are structured tourge the developing frame 241 downward as the press actuation mechanisms241 k are pressed down by the pressing portions 241 g 2. The pressactuation mechanisms 241 k will be described in detail below.

A pair of guide projections 241 m is formed on upper portions of a rearside of the developing frame 241. Each guide projection 241 m has aguide surface 241 m 1 formed into a substantially flat shape.

2. Detailed Structure of Removably Installing Developing Cartridge andPhotoconductive Unit

FIG. 31 is a perspective overhead view of the process cartridge 230shown in FIG. 26. FIG. 31 shows that one of the four developingcartridges 240 is removed from the process cartridge 230. FIG. 32 is apartially enlarged perspective view of the drum unit 250 shown in FIG.31. More specifically, FIG. 32 is an enlarged perspective view showingone end portion of the drum unit 250, with respect to its widthdirection, from which one developing cartridge 240 is removed. FIGS. 33Aand 33B are perspective views of the drum unit 250 shown in FIG. 31,viewed from a side at an angle. FIGS. 34A and 34B are perspective viewsof the drum unit 250 shown in FIG. 31, viewed from a side at an angleopposite to the side shown in FIGS. 33A and 33B.

Referring to FIG. 31, the process cartridge 230 includes four sets ofthe developing cartridges 240 and the drum units 250 that are arrangedalong the front-rear direction L. The developing cartridges 240 and thedrum units 250 are installed in a process cartridge frame 230 a.

The process cartridge frame 230 a includes a pair of side frames 232, afront beam 233 and a rear beam 234. The front beam 233 is disposed atfront ends (right side in FIG. 31) of the side frames 232 between theside frames 232. The rear beam 234 is disposed at rear ends (left sidein FIG. 31) of the side frames 232 between the side frames 232. In asubstantially rectangular area, in plan view, defined by the side frames232, the front beam 233 and the rear beam 234, the four drum units 250are fixed. The developing cartridges 240 may be installed in the processcartridge frame 230 a via the drum units 250.

Coupling exposure holes 232 a, as through holes, are formed atsubstantially central portions of the side frame 232 with respect to itsheight direction. The coupling exposure hole 232 a is structured toexpose the coupling part 248 a outward of the process cartridge frame230 a, through the coupling exposure hole 232 a when the developingcartridge 240 is installed in the process cartridge frame 230 a.

A guide rib 232 b is formed on an upper end of each side frame 232. Theguide rib 232 b extends outward in the width direction W. The guide rib232 b has a length parallel to the front-rear direction L. Side frameguide rollers 232 c are rotatably supported at the rear end portions ofthe side frames 232 just below the guide ribs 232 b.

The side frames 232 are structured to guide the installation and removalof the process cartridge 230 along the front-rear direction L, by makingthe guide ribs 232 b and the side frame guide rollers 232 c slide on theslide guide frames 211 c (in FIG. 26) of the main body casing 211.

A front beam handle 233 a is formed on an upper end of the front beam233 at a central portion thereof with respect to the width direction W.A rear beam handle 234 a is formed on an upper end of the rear beam 234at a central portion thereof with respect to the width direction W. Thefront beam handle 233 a and the rear beam handle 234 a extend upward soas to form an inverted U shape such that a user can hold the handles 233a, 234 a when the process cartridge 230 removed from the main bodycasing 211 (in FIG. 26) is handled.

A pair of rear beam guide rollers 234 b is rotatably supported at eachend of the rear beam 234. The rear beam guide roller 234 b and the sideframe guide roller 232 c are arranged along the front-rear direction L.The rear beam guide rollers 234 b are structured to operate similar tothe side frame guide rollers 232 c.

(1) Detailed Structure of Drum Unit

A drum frame 251 is supported by a pair of the side frames 232. The drumframe 251 includes a right side wall 251 a, a bottom wall 251 b, and aleft side wall 251 e. An area defined by the right side wall 251 a, thebottom wall 251 b, and the left side wall 251 e is formed as adeveloping cartridge installation portion 250 a in which the developingcartridge 240 is installed. A photoconductive drum 252 is rotatablysupported below the developing cartridge installation portion 250 abetween the right side wall 251 a and the left side wall 251 e.

Referring to FIGS. 31 and 32, the right side wall 251 a is fixed, forexample, by a screw to one of the side frames 232 (upper side frame inFIG. 31). An upward-open collar positioning guide groove 251 a 1 isformed on the right side wall 251 a. A collar positioning accommodationbase 251 a 2 is formed at a lower end of the collar positioning guidegroove 251 a 1. The collar positioning accommodation base 251 a 2 isformed substantially straightly toward the photoconductive drum 252along a guiding direction Z, as shown by an arrow in FIG. 32. An end ofa drum shaft 252 a of the photoconductive drum 252 is exposed outsidethe side frame 232 for grounding.

As shown in FIGS. 33A and 33B, the collar positioning guide groove 251 a1 is formed to guide the collar member 246, which is disposed on an endof the developing cartridge 240, in the substantially verticaldirection. As shown in FIG. 33B, the collar positioning accommodationbase 251 a 2 is formed to perform positioning of the developingcartridge 240 and the drum unit 250 as the collar positioningaccommodation base 251 a 2 contacts the collar member 246. Morespecifically, when the collar member 246 is guided in the collarpositioning accommodation base 251 a 2 along the guiding direction Z andcontacts the lower end of the collar positioning accommodation base 251a 2, the developing roller shaft 244 a and the drum shaft 252 a areplaced in position. Thus, the positional relation between the developingroller 244 and the photoconductive drum 252 can be set properly to apredetermined state.

Referring to FIGS. 31 and 32, a developing cartridge insertion roller257 is rotatably supported at each upper end of the bottom wall 251 bwith respect to the width direction W. The developing cartridgeinsertion rollers 257 are structured to guide the installation of thedeveloping cartridge 240 in the developing cartridge installationportion 250 a along the guiding direction Z, as shown in FIG. 32, bycontacting to the guide surfaces 241 m 1 of the guide projections 241 m(in FIG. 28) provided in the developing cartridge 240.

Referring to FIG. 31, the left side wall 251 e is fixed, for example, bya screw to the other one of the side frames 232 (lower side frame inFIG. 31). An upward-open coupling part guide groove 251 e 1 is formed onthe left side wall 251 e. The coupling part guide groove 251 e 1 isformed to guide the input opening portion 248 a 2 of the coupling part248 a, which is provided on the other end of the developing cartridge240, along the substantially vertical direction.

Referring to FIGS. 34A and 34B, a coupling accommodation base 251 e 2 isformed at a lower end of the coupling part guide groove 251 e 1. Asshown in FIG. 34B, the coupling accommodation base 251 e 2 is formed toperform positioning of the developing cartridge 240 and the drum unit250 as the coupling accommodation base 251 e 2 contacts the inputopening portion 248 a 2. In other words, when the input opening portion248 a 2 is accommodated in the coupling accommodation base 251 e 2, thedeveloping roller shaft 244 a and the drum shaft 252 a may be placed inposition.

A developing roller shaft end accommodating portion 251 e 3 is formedbelow the coupling accommodation base 251 e 2. The developing rollershaft end accommodating portion 251 e 3 is structured to receive an endof the developing roller shaft 244 a when the input opening portion 248a 2 is accommodated in the coupling accommodation base 251 e 2.

Referring to FIGS. 33A to 34B, the width of at least a lower half of thecollar positioning guide groove 251 a 1 is set smaller than that of thecoupling part guide groove 251 e 1. In other words, the collarpositioning guide groove 251 a 1 is formed to have such a width thatdoes not accommodate the input opening portion 248 a 2 in the baseportion of the collar positioning guide groove 251 a 1, that is, in thecollar positioning accommodation base 251 a 2.

(2) Structure of Feeding Power to Developing Roller

Referring to FIGS. 33A and 33B, a developing bias terminal 258, as arelay-electrode member (feeding member), is provided on an outer surfaceof the right side wall 251 a. The developing bias terminal 258 includesa base 258 a, a fixed part 258 b, and a movable part 258 c, which areintegrally formed by bending a wire.

The base 258 a is formed into a coiled shape with two or three loops.The fixed part 258 b and the movable part 258 c are connected to ends ofthe base 258 a. The base 258 a and the fixed part 258 b are engaged withthe outer surface of the right side wall 251 a and fixed thereon. Thefixed part 258 b is structured and disposed such that it may beelectrically connected, when the drum units 250 are installed in themain body casing 211 (in FIG. 26), to a power feed output electrodeprovided in the main body casing 211.

The movable part 258 c is structured to elastically pivot about the base258 a. The developing bias terminal 258 is disposed such that themovable part 258 c is exposed in the collar positioning guide groove 251a 1. As shown in FIG. 33B, the movable part 258 c contacts the terminalportion 247 b while the movable part 258 c and the terminal portion 247b press each other, when the developing cartridge 240 is set with thedrum unit 250. Thus, the movable part 258 c may be electricallyconnected to the terminal portion 247 b.

3. Detailed Structure of Pressing Developing Cartridge TowardPhotoconductive Drum

FIG. 35A is a side view of the developing cartridge 240, shown in FIG.27, in a non-pressing (retracted) state (position). FIG. 35B is a sideview of the developing cartridge 240, shown in FIG. 27, in a pressingstate (position). FIG. 36A is an enlarged cross-sectional side view ofthe press actuation mechanism 241 k in the non-pressing state(position), viewed from a side opposite to the side shown in FIG. 35A.FIG. 36B is an enlarged cross-sectional side view of the press actuationmechanism 241 k in the pressing state (position), viewed from a sideopposite to the side shown in FIG. 35B. FIG. 37A is a side view of thedeveloping cartridge 240 in the pressing state (position), viewed from aside opposite to the side shown in FIG. 35B. FIG. 37B is an explanatoryschematic showing forces exerted on the developing cartridge 240 in thepressing state (position) shown in FIG. 37A.

Referring to FIGS. 35A and 35B, the press actuation mechanisms 241 k arestructured such that the developing frame 241 may be elastically urgedtoward the guiding direction Z, based on a very little pivotal movementof the holding portion 241 g about hinges 241 h in the clockwisedirection in FIGS. 35A and 35B. In other words, the press actuationmechanisms 241 k are structured to convert the downward movement of thepressing portions 241 g 2 exerted when the pressed bosses 241 g 1disposed on the free-end side of the holding portion 241 g are presseddown, into a force for elastically urging the developing frame 241 alongthe guiding direction Z.

The guide surfaces 241 m 1 of the guide projections 241 m make slidablecontact with the developing cartridge insertion rollers 257, so that thedeveloping frame 241 may be guided along the guiding direction Z.

Referring to FIGS. 36A and 36B, each press actuation mechanism 241 kincludes a movement member 241 k 1, a guide cylinder 241 k 2, and adeveloping cartridge urging spring 241 k 3.

The movement member 241 k 1 is accommodated in the guide cylinder 241 k2, which is formed into a substantially cylindrical shape. The movementmember 241 k 1 may reciprocate in the substantially vertical directionalong an axis of the guide cylinder 241 k 2.

The developing cartridge urging spring 241 k 3 is disposed between themovement member 241 k 1 and the upper wall 241 c of the developing frame241. The developing cartridge urging spring 241 k 3 is structured tourge the movement member 241 k 1 substantially upward. In other words,the developing cartridge urging spring 241 k 3 is structured to urge orpress the upper wall 241 c of the developing frame 241 substantiallydownward when the movement member 241 k 1 is pressed substantiallydownward, as shown in FIG. 36B. In this aspect, an action point(pressing position PP), where the downward pressing (urging) by thedeveloping cartridge urging spring 241 k 3 is acted on the upper wall241 c, is provided at an intersection of the upper wall 241 c and theaxial line of the developing cartridge urging spring 241 k 3.

A hook 241 k 4 is formed on a lower end of the movement member 241 k 1,so as to extend outward. The hook 241 k 4 is movable along thesubstantially vertical direction in a hook movement guide slit 241 k 5formed in the guide cylinder 241 k 2. An upper end of the hook movementguide slit 241 k 5 is closed by a hook stopper 241 k 6. Morespecifically, as the hook 241 k 4 contacts the hook stopper 241 k 6, themovement member 241 k 1 can be prevented from being separated from theguide cylinder 241 k 2.

Referring to FIGS. 37A and 37B, the guide surface 241 m 1 of the guideprojection 241 m is formed to have a surface parallel to a pressingaction line Y connecting a pressing position PP, which is the actionpoint, and a contact position (developing position) CP. Morespecifically, the pressing action line Y is set parallel to the collarpositioning accommodation base 251 a 2 (guiding direction Z).

In this aspect, an angle formed between a developing cartridge pressingdirection X at the pressing position PP and the pressing action line Yis about 20 degrees. Thus, the guide surfaces 241 m 1 of the guideprojections 241 m are set to press the developing cartridge insertionrollers 257 (FIGS. 35A and 35B) at a predetermined force.

In this aspect, the movable part 258 c of the developing bias terminal258 includes a feeding member opposing portion 258 c 1 formed straightlyat a position facing the terminal portion 247 b. The developing biasterminal 258 is structured such that the feeding member opposing portion258 c 1 is parallel to the pressing action line Y and the guidingdirection Z, when the developing cartridge 240 is pressed, that is, whenthe toner carrying peripheral surface 244 b of the developing roller 244and an image carrying peripheral surface 252 b of the photoconductivedrum 252 contact with each other at the contact position CP at apredetermined pressure.

In this aspect, the developing bias terminal 258 is structured such thata direction (feeding member pressing direction) S in which the feedingmember opposing portion 258 c 1 of the movable part 258 c of thedeveloping bias terminal 258 and the terminal portion 247 b of theelectrode member 247 press each other, is set substantiallyperpendicular to the pressing action line Y and the guiding direction Z.More specifically, the angle formed between the direction S and thepressing action line Y/the guiding direction Z is set to about 90degrees (e.g., between 89 and 91 inclusive).

FIG. 38 is an enlarged side view showing a periphery of the terminalportion 247 b shown in FIG. 37A. In FIG. 38, the coupling part 248 aprovided on the developing frame 241 opposite side of the terminalportion 247 b and a coupling drive gear 283, as a second cylindricalportion, provided concentrically with the coupling part 248 a, areindicated in double dashed chain lines.

Referring to FIG. 38, the driven coupling part 248 a 1 of the couplingpart 248 a is formed to have a larger outside diameter than that of asmall diameter portion 246 a of the collar member 246 and the terminalportion 247 b. The outer shape of the driven coupling part 248 a 1 andthe coupling drive gear 283 is formed to include a feeding memberpressing position SP when viewed from a side along the longitudinaldirection of the developing cartridge 240. At the feeding memberpressing position SP, the terminal portion 247 b contacts the feedingmember opposing portion 258 c 1 of the movable part 258 c of thedeveloping bias terminal 258. In this aspect, the coupling part 248 aand the coupling drive gear 283 are structured such that the feedingmember pressing position SP substantially matches with the axis of thedriven coupling part 248 a 1 and the coupling drive gear 283.

4. Detailed Structure of Selectively Pressing the Developing Cartridges

FIG. 39 is an enlarged perspective view showing a periphery of theprocess cartridge 230 shown in FIG. 26. FIG. 40 is an enlargedperspective view showing a periphery of the slide guide frames 211 c andthe linear cam mechanisms 219 shown in FIG. 26. FIG. 40 shows theprocess cartridge 230 removed from FIG. 39.

Referring to FIG. 39, the slide guide frames 211 c are structured tosupport each end of the process cartridge 230 with respect to its widthdirection W, and upper ends of the process cartridge 230 with respect toits height direction. Each of the slide guide frames 211 c includes aslide rail 211 c 1 and a slide guide roller 211 c 2.

As shown in FIG. 39, the slide rails 211 c 1 are structured to engagewith the upper ends of the side frames 232 (i.e., the guide ribs 232 bin FIG. 31) when the process cartridge 230 is installed in the main bodycasing 211. The slide rails 211 c 1 and the slide guide rollers 211 c 2are structured to guide the movement of the process cartridge 230 in thefront-rear direction L, in cooperation with the side frames 232 of theprocess cartridge 230 (side frame guide rollers 232 c and guide ribs 232b in FIG. 31) and the rear beam guide rollers 234 b.

Each linear cam mechanism 219 includes a bar cam member 219 a, as aliner cam member, a cam supporting frame 219 b, a pinion gear 219 c, anda gear shaft 219 d.

The bar cam member 219 a is a cam formed to have a length parallel tothe front-rear direction L. The bar cam member 219 a is disposed andstructured to reciprocate along the front-rear direction L. Morespecifically, a rack gear 219 a 2 is formed on an upper surface of a cambase end 219 a 1, which is provided on the rear side of the bar cammember 219 a. The rack gear 219 a 2 is structured to engage with thepinion gear 219 c.

A pair of the pinion gears 219 c is directly connected by the gear shaft219 d, so as not rotate relative to each other. A pair of the piniongears 219 c and the gear shaft 219 d are structured such that when oneof the bar cam members 219 d is moved in the front-rear direction L by adrive source (not shown) provided in the main body casing 211, the oneof the bar cam members 219 d and the other one of the bar cam members219 d may be synchronously reciprocated in the front-rear direction L inphase with each other (with respect to the position in the front-reardirection L).

FIG. 39 illustrates the left bar cam member 219 a that is moved to therearmost position and the right bar cam member 219 a that is moved to amiddle position. This illustration is provided only for the purpose ofdescribing that the bar cam members 219 are movable along the front-reardirection L. It should be noted that the linear cam mechanisms 219 aremoved in synchronization with each other and the situation such as shownin FIG. 39 will not occur in actuality.

The cam supporting frame 219 b includes a cam supporting frame base 219b 1, a cam supporting frame upper plate 219 b 2, a cam supporting frameside plate 219 b 3, and a cam supporting frame bottom plate 219 b 4,which are integrally formed of a metal plate.

The cam supporting frame base 219 b 1 is provided to extend upwardly inthe vertical direction from an outer end of the supporting frame upperplate 219 b 2, with respect to its width direction W. The cam supportingframe base 219 b 1 is fixed to an inner wall of the main body casing 211using, for example, a screw, so that the cam supporting frame 219 b maybe supported on the inner side of the main body casing 211.

The cam supporting frame side plate 219 b 3 is provided to extenddownwardly in the vertical direction from an inner end of the supportingframe upper plate 219 b 2, with respect to its width direction W. Thecam supporting frame bottom plate 219 b 4 is provided to extend outwardin the width direction W from a lower end of the cam supporting frameside plate 219 b 3. The bar cam member 219 a is disposed in a spacedefined by the cam supporting frame upper plate 219 b 2, the camsupporting frame side plate 219 b 3, and the cam supporting frame bottomplate 219 b 4.

Boss accommodating openings 219 b 5 are formed on the cam supportingframe upper plate 219 b 2 and the cam supporting frame side plate 219 b3. As shown in FIG. 39, the boss accommodating openings 219 b 5 arestructured to make the separation bosses 241 f and the pressed bosses241 g 1 of the developing cartridges 240 oppose the bar cam member 219 awhen the process cartridge 230 is installed in the main body casing 211.

FIG. 41 is a perspective view of a pair of the bar cam members 219 ashown in FIG. 40. Referring to FIGS. 40 and 41, each bar cam member 219a is provided with, for example, four supplementary cam members 219 e.

Referring to FIG. 40, the supplementary cam members 219 e are disposedopposite to the boss accommodating openings 219 b 5. The supplementarycam member 219 e is pivotally structured about a supplementary cam pivotpin 219 e 1 parallel to the width direction W. An inner end of thesupplementary cam pivot pin 219 e 1 with respect to the width directionW is supported in a through hole formed directly below the bossaccommodating opening 219 b 5 on the cam supporting frame side plate 219b 3. In other words, the supplementary cam member 219 e is supported soas not move in the front-rear direction L by the through hole formed onthe cam supporting frame side plate 219 b 3.

Referring to FIG. 41, an apostrophe ‘ is provided to the referencenumber of the foremost supplementary cam member 219 e for the clarity ofthe description. The foremost supplementary cam members 219 e’ have thesame structure as other supplementary cam members 219 e, expect that theforemost supplementary cam members 219 e′ are moved in the differenttiming than the other supplementary cam members 219 e when the bar cammembers 219 a move in the front-rear direction L, as will be describedin detail below. Similarly, an apostrophe (′) is provided to thereference numbers of the foremost components of the bar cam member 219a, in association with the foremost supplementary cam member 219 e′.

A thin plate of a supplementary cam guide wall 219 a 3, which definesthe outside wall of the bar cam member 219 a with respect to the widthdirection W, has, for example, four elongated supplementary cam guideopenings 219 a 4 having a length parallel to the front-rear direction L.The supplementary cam guide openings 219 a 4 having the same shape aredisposed along the front-rear direction L. The supplementary cam member219 e is provided with a supplementary cam pivot projection 219 e 2 thatextends outward in the width direction W. The supplementary cam pivotprojection 219 e 2 is inserted into the supplementary cam guide opening219 a 4.

More specifically, the supplementary cam member 219 e is pivotallysupported in the through hole formed on the cam supporting frame sideplate 219 b 3 (FIG. 40) and the supplementary cam guide opening 219 a 4.The supplementary cam member 219 e is supported so as to move relativeto the bar cam member 219 a along the longitudinal direction of thesupplementary cam guide opening 219 a 4, when the bar cam members 219 aare reciprocated in the front-rear direction L. As shown in FIGS. 40 and41, the supplementary cam guide openings 219 a 4 are formed such thatthe position of the supplementary cam pivot projection 219 e 2, withrespect to the front-rear direction L, in each of four supplementary camguide openings 219 a 4 becomes substantially the same. In other words,the relative positional relation between the supplementary cam guideopening 219 a 4 and the supplementary cam member 219 e is all the samein the four sets of the supplementary cam guide openings 219 a 4 and thesupplementary cam members 219 e.

Referring to FIG. 41, the supplementary cam guide wall 219 a 3, whichdefines the outside wall of the bar cam member 219 a, is formed withsupplementary cam supporting portions 219 a 5 that extend inward in thewidth direction W from the lower end of the supplementary cam guide wall219 a 3. The supplementary cam supporting portion 219 a 5 is structuredto support the supplementary cam member 219 e from below. Thesupplementary cam supporting portions 219 a 5 are formed at positionsassociated the supplementary cam guide openings 219 a 4.

A supplementary cam contact wall 219 a 6 is formed to extend upward fromthe front end of the supplementary cam supporting portion 219 a 5. Thesupplementary cam contact wall 219 a 6 is structured to contact thesupplementary cam member 219 e when the bar cam members 219 a are movedtoward the rear side. The relative positional relation between thesupplementary cam contact wall 219 a 6 and the supplementary cam member219 e (supplementary cam pivot projection 219 e 2) is also all the samein the four sets of the supplementary cam contact walls 219 a 6 and thesupplementary cam members 219 e (supplementary cam pivot projections 219e 2).

A supplementary cam exposure opening 219 a 7 that opens downward isformed behind the rear end of the supplementary cam supporting portion219 a 5. A pressing portion 219 a 8 for the pressed boss 241 g 1 isformed to extend forwardly from the upper end of the supplementary camcontact wall 219 a 6. As will be described below, the pressing portions219 a 8 are structured to contact the pressed bosses 241 g 1 when thebar cam members 219 a are moved frontward, thereby pressing the pressedbosses 241 g 1 (FIG. 39) downward.

The length of the supplementary cam supporting portion 219 a 5 parallelto the front-rear direction L is set shorter than that of thesupplementary cam guide opening 219 a 4. In other words, the rear end ofsupplementary cam guide opening 219 a 4 is disposed above thesupplementary cam exposure opening 219 a 7. The foremost supplementarycam supporting portion 219 a 5′ is formed shorter than the othersupplementary cam supporting portions 219 a 5. The foremost pressingportion 219 a 8′ is formed longer than the other pressing portions 219 a8.

FIG. 42A is an enlarged perspective view of the supplemental cam member219 e, shown in FIG. 41, in a turned state. FIG. 42B is an enlargedperspective view of the supplemental cam member 219 e, shown in FIG. 41,in an upright state. The supplementary cam member 219 e can take twostates by pivoting about the supplementary cam pivot projection 219 e 2,that is, the turned state, as shown in FIG. 42A, and the upright state,as shown in FIG. 42B.

A separation boss mounting slope 219 e 3 that slants slightly is formedon an upper end (top) of the supplementary cam member 219 e when placedin the upright state, as shown in FIG. 42B. A protrusion is formed onthe rear end (upper right end in FIG. 42B) of the separation bossmounting slope 219 e 3. The front end of the separation boss mountingslope 219 e 3 is formed to have a smoothly-curved or chambered surfaceto allow the separation boss 241 f to readily mount on the separationboss mounting slope 219 e 3 when the separation boss 241 f contacts theslope 219 e 3.

A first supplementary cam projection 219 e 4 and a second supplementarycam projection 219 e 5 are formed to extend downward from a lower end ofthe supplementary cam member 219 e when placed in the upright state, asshown in FIG. 42B. The first supplementary cam projection 219 e 4 andthe second supplementary cam projection 219 e 5 are disposed indifferent positions with respect to their width direction (axialdirection of the supplementary cam pivot projection 219 e 2). Morespecifically, the first supplementary cam projection 219 e 4 is disposedmore inward than the second supplementary cam projection 219 e 5 withrespect to the width direction W in FIG. 41 (lower right side in FIG.42B).

FIG. 43A is an enlarged perspective view of the bar cam member 219 a andthe supplemental cam members shown in FIG. 41, wherein the bar cammember 219 a is in the foremost position. FIG. 43B is an enlargedperspective view of the bar cam member 219 a and the supplemental cammembers 219 e shown in FIG. 41, wherein the bar cam member 219 a is inthe rearmost position. As described above, the position of thesupplementary cam member 219 e (supplementary cam pivot projection 219 e2) with respect to the front-rear direction L is fixed, even when thebar cam members 219 a are moved.

FIGS. 44-46 are cross-sectional side views of the bar cam member 219 aand the supplemental cam members 219 e shown in FIGS. 43A and 43B. FIG.44 shows the bar cam member 219 a and the supplemental cam members 219 ewhen the bar cam member 219 a is in the rearmost position (right side inFIG. 44). FIG. 45 shows the bar cam member 219 a and the supplementalcam members 219 e when the bar cam member 219 a is in a middle position.FIG. 46 shows the bar cam member 219 a and the supplemental cam members219 e when the bar cam member 219 a is in the foremost position (leftside in FIG. 46). FIGS. 47-49 are enlarged side views of the developingcartridges 240 and the linear cam mechanisms 219 shown in FIG. 39. Frontand rear sides in FIGS. 44-46 are reversed in FIGS. 47-49. In otherwords, FIGS. 44-46 show cross-sections of the bar cam member 219 a andthe supplemental cam members 219 e when viewed from the side opposite tothe side of the developing frame 241 shown in FIGS. 47-49. FIG. 44corresponds to FIG. 47. FIG. 45 corresponds to FIG. 48. FIG. 46corresponds to FIG. 49.

Referring to FIGS. 43A and 43B, the rear end (right side in FIGS. 43Aand 43B) of the supplementary cam supporting portion 219 a 5 isstructured to contact the first supplementary cam projection 219 e 4 ofthe supplementary cam member 219 e. A protrusion 219 a 9 for pivotingsupplementary cam member 219 e is formed on the outer side of thesupplementary cam supporting portion 219 a 5 with respect to its widthdirection, behind the rear end of the supplementary cam supportingportion 219 a 5. The protrusion 219 a 9 is disposed to extend upward ata position associated with the second supplementary cam projection 219 e5 of the supplementary cam member 219 e with respect to its widthdirection (at a position where the protrusion 219 a 9 can contact thesecond supplementary cam projection 219 e 5).

Referring to FIGS. 43A through 46, the bar cam members 219 a and thesupplementary cam members 219 e are structured such that thesupplementary cam members 219 e pivot in the clockwise direction in thedrawings, placing the supplementary cam members 219 e in the turnedstate, when the bar cam members 219 a are moved to the front side (leftside in the drawings), that is, when the supplementary cam members 219 eare moved to the rear side relative to the bar cam members 219 a. Morespecifically, the protrusion 219 a 9 is formed to pivot thesupplementary cam member 219 e by making contact with the secondsupplementary cam projection 219 e 5, when the bar cam members 219 a aremoved toward the front side. (The pivotal movement of the supplementarycam members 219 e may be readily understood when FIGS. 44, 45 and 46 arereferred to in this order.) When the supplementary cam member 219 e isin the turned state, the supplementary cam member 219 e is disposedabove the supplementary cam exposure opening 219 a 7.

The foremost protrusion 219 a 9′ is formed at a substantially centralportion with respect to the front-rear direction of the foremostsupplementary cam guide opening 219 a 4′. Other protrusions 219 a 9 areformed nearer to the rear ends of the supplementary cam guide openings219 a 4. In other words, positions of the foremost protrusion 219 a 9′and other protrusion 219 a 9′ are set such that the foremostsupplementary cam member 219 e′ is first placed in the turned stateprior to the other supplementary cam members 219 e when the bar cammembers 219 a are moved to the front side.

As described above, the pressing portion 219 a 8 is structured to pressthe pressed boss 241 g 1 by mounting thereon when the bar cam member 219a is moved toward the front side. More specifically, the front end ofthe pressing portion 219 a 8 has a slanted portion, so that the pressingportion 219 a 8 can readily mount on the pressed boss 241 g 1 when thepressing portion 219 a 8 makes contact with the pressed boss 241 g 1.The foremost pressing portion 219 a 8′ is formed longer than the otherpressing portions 219 a 8 to first press the foremost pressed boss 241 g1, prior to the other pressed bosses 241 g 1.

The bar cam members 219 a and the supplementary cam members 219 e arestructured such that the supplementary cam members 219 e pivot in thecounterclockwise direction in the drawings, placing the supplementarycam members 219 in the upright state, when the bar cam members 219 a aremoved to the rear side (right side in the drawings), that is, when thesupplementary cam members 219 e are moved to the front side relative tothe bar cam members 219 a. More specifically, the first supplementarycam projection 219 e 4 is formed and disposed to pivot the supplementarycam member 219 e by making contact with the rear end of thesupplementary cam supporting portion 219 a 5 when the bar cam members219 a is moved toward the rear side. (The pivotal movement of thesupplementary cam member 219 e may be readily understood when FIGS. 46,45 and 44 are referred to in this order.) The supplementary cam member219 e placed in the upright state is supported on the upper side of thesupplementary cam supporting portion 219 a 5.

As described above, the foremost supplementary cam supporting portion219 a 5′ is formed shorter than the other supplementary cam supportingportions 219 a 5. In other words, lengths of the foremost supplementarycam supporting portion 219 a 5′ and the other supplementary camsupporting portions 219 a 5 are set such that the foremost supplementarycam member 219 e′ is placed in the upright state later than the othersupplementary cam members 219 e when the bar cam members 219 a are movedto the rear side.

As shown in FIGS. 47 through 49, the bar cam members 219 a arestructured to urge the developing cartridges 240 (black, cyan, magenta,and yellow developing cartridges 240K, 240C, 240M, 240Y), which arearranged in the front-rear direction L, toward the respectivephotoconductive drums 252 disposed therebelow, by pressing the pressedbosses 241 g 1 downward, in accordance with the movement of the bar cammembers 219 a in the front-rear direction L. The supplementary cammembers 219 e are structured to maintain the developing cartridges 240(black, cyan, magenta, and yellow developing cartridges 240K, 240C,240M, 240Y) in a predetermined retracted state by separating thedeveloping rollers 244 from the photoconductive drums 252. This may beachieved by placing the supplementary cam members 219 e in the uprightstate to raise the separation bosses 241 f, in accordance with themovement of the bar cam members 219 a in the front-rear direction L.

Further, the bar cam members 219 a and the supplementary cam members 219e (supplementary cam members 219 e′) are structured to urge only theblack developing cartridge 240K toward the photoconductive drum 252 andto maintain the other developing cartridges 240C, 240M, 240Y in theretracted state, in accordance with the movement of the bar cam members219 a in the front-rear direction L.

5. Structure for Transmitting Drive Force

FIGS. 50 and 51 are bottom views of the developing cartridges 240 and adrive force transmission mechanism 280 for transmitting drive forcethereto provided in the main body casing 211 shown in FIG. 26. Referringto FIGS. 50 and 51, the drive force transmission mechanism 280 includesa drive coupling part 281, a drive coupling part urging spring 282, adrive coupling gear 283, a drive coupling movement cam 284, a motor 285,and a gear train 286.

Four drive coupling parts 281 are provided along the front-reardirection L (up-down direction in FIGS. 50 and 51) in association withthe coupling parts 248 a of the four developing cartridges 240. Thedrive coupling part 281 includes a coupling engagement shaft 281 a, anda flange portion 281 b.

The coupling engagement shaft 281 a is inserted from its tip end intothe coupling part 248 a, so that the coupling engagement shaft 281 a maybe engaged with the coupling part 248 a. As the coupling engagementshaft 281 a and the coupling part 248 a are structured to transmit driveforce to the developing cartridge 240 from the drive force transmissionmechanism 280 by engaging with each other. The flange portion 281 b isformed at a base end (right end in FIGS. 50 and 51) of the couplingengagement shaft 281 a.

The drive coupling part urging spring 282 is disposed such that its oneend contacts the flange portion 281 b and the other end contacts thedrive coupling gear 283. The drive coupling part urging spring 282 isstructured to urge the flange portion 281 b (drive coupling part 281)toward the coupling part 248 a.

The drive coupling gear 283 is structured to rotate together with thedrive coupling part 281. More specifically, the drive coupling part 281and the drive coupling gear 283 are structured so as not to moverelative to each other in their rotating direction, by engaging a shaft(axis) of the drive coupling gear 283 in an engagement hole formed inthe coupling engagement shaft 281 a (axis of the drive coupling part281).

Further, the drive coupling part 281 and the drive coupling gear 283 arestructured to move relative to each other in their axial direction. Morespecifically, the drive coupling part 281 and the drive coupling gear283 are structured such that the shaft (axis) of the drive coupling gear283 may slide in the engagement hole formed in the coupling engagementshaft 281 a (axis of the drive coupling part 281) along the axialdirection.

The drive coupling movement cam 284 is structured to position the fourdrive coupling parts 281 arranged along the front-rear direction L, withrespect to their axial direction (width direction W). The drive couplingmovement cam 284 includes four sets of a cam bottom face 284 a, a camtop face 284 b, and a cam slanted face 284 c.

As shown in FIG. 50, the cam bottom face 284 a is formed to contact theflange portion 281 of the drive coupling part 281, which is located at aposition to engage with the coupling part 248 a. As shown in FIG. 51,the cam top face 284 b is formed to contact the flange portion 281 ofthe drive coupling part 281, which is located at a position away fromthe coupling part 248 a. The cam slanted face 284 c is formed tosmoothly connect the cam bottom face 284 a and the cam top face 284 b.

The drive coupling movement cam 284 is structured to gradually move theflange portion 281 b outwardly with respect to the width direction W(toward the right side in FIG. 50) along the cam slanted face 284 c,against a pressing force of the drive coupling part urging spring 282,when the drive coupling movement cam 284 is moved downward from theposition shown in FIG. 50 by a solenoid and a cam mechanism (not shown).The drive coupling movement cam 284 is structured to move the drivecoupling part 281, to a retracted position, as shown in FIG. 51.Further, the drive coupling movement cam 284 is structured to move thedrive coupling part 281 to an engagement position, as shown in FIG. 50,with the pressing force of the drive coupling part urging spring 282,when the drive coupling movement cam 284 is moved upward from a positionshown in FIG. 51 by a solenoid (not shown), etc.

The gear train 286 is structured to transmit the drive force generatedby the motor 285 to the four drive coupling gears 283.

6. Description of Operations According to Structures of Aspects

Next, operations performed when the process cartridge 230 is installedin or removed from the main body casing 211 of the color laser printer210 shown in FIG. 26, will be described with reference to theaccompanying drawings.

(1) Installation/Removal of the Developing Cartridge

Referring to FIGS. 30 and 31, when the developing cartridge 240 isremoved from the process cartridge frame 230 a of the process cartridge230, a user may hold the central portion, with respect to thelongitudinal direction of the developing cartridge 240, of the holdingportion 241 g provided at the upper potion of the developing cartridge240. Thus, the holding portion 241 g is brought into an uprightposition, as shown in FIG. 30. Then, as the user pulls up the holdingportion 241 g, which has been placed in the upright position, thedeveloping cartridge 240 is moved upward while being guided by thecollar positioning guide groove 251 a 1 and the coupling part guidegroove 251 e 1 formed at each end of the drum frame 251, with respect tothe width direction W. Thus, the developing cartridge 240 is removedfrom the drum unit 250.

When the developing cartridge 240 is installed in the process cartridgeframe 230 a, the holding portion 241 g is placed in a turned or restposition, as shown in FIGS. 33A through 34B, and the central portion ofthe upper end of the developing cartridge 240, with respect to thelongitudinal direction of the developing cartridge 240, may be held. Asshown in FIG. 33A, the collar member 246 is inserted into the collarpositioning guide groove 251 a 1, and as shown in FIG. 34A, the inputopening portion 248 a 2 is inserted into the coupling part guide groove251 e 1.

In this state, as the developing cartridge 240 is pressed furtherdownward, the collar member 246 is received in the collar positioningaccommodation base 251 a 2, as shown in FIG. 33B, and the input openingportion 248 a 2 is inserted into the coupling accommodation base 251 e2, as shown in FIG. 34B. Further, an end of the developing roller shaft244 a on which the collar member 246 is not mounted, is received in thedeveloping roller shaft end accommodating portion 251 e 3.

Referring to FIGS. 32 through 33B, the movable part 258 c of thedeveloping bias terminal 258 is exposed in the collar positioning guidegroove 251 a 1, so that the movable part 258 may first contact thecollar member 246. Thus, the movable part 258 c is pressed down by thecollar member 246 and moved to the left side in FIGS. 33A and 33B(counterclockwise direction in FIGS. 33A and 33B). Then, the movablepart 258 contacts the terminal portion 247 b.

In this aspect, when the developing cartridge 240 is installed in theprocess cartridge frame 230 a, the movable part 258 c exposed in thecollar positioning guide groove 251 a 1 is pressed and moved down by thecollar member 246 and then contacts the terminal portion 247 b. Thus,electrical connection by the contact between the terminal portion 247 band the developing bias terminal 258 may be smoothly and reliablyestablished when the developing cartridge 240 is installed in theprocess cartridge frame 230 a.

Referring to FIGS. 32 through 33B, the lower half of the collarpositioning guide groove 251 a 1 is formed smaller than the couplingpart guide groove 251 e 1. Therefore, even when the developing cartridge240 is mis-oriented and the input opening portion 248 a 2 is inserted,by mistake, into the collar positioning guide groove 251 a 1, theinsertion of the input opening portion 248 a 2 is stopped at an upperportion of the collar positioning guide groove 251 a 1. Thus,inappropriate installation of the developing cartridge 240 relative tothe drum unit 250 may be reliably prevented.

(2) Urging/Pressing of Developing Cartridge Toward Photoconductive Drum

Referring to FIGS. 35A and 35B, when the developing cartridge 240 placedin the non-pressing (retracted) state, as shown in FIG. 35A, is broughtinto the pressing state, as shown in FIG. 35B, in which an image can beformed, the pressed bosses 241 g 1 are pressed down. Accordingly, theholding portion 241 g is slightly moved pivotally about the hinges 241 hin the clockwise direction in FIGS. 35A and 35B. By the pivotal movementof the holding portion 241 g, the pressing portions 241 g 2 on the freeend side of the holding portion 241 g is moved downward. Thus, forcethat elastically urges the developing frame 241 along the guidingdirection Z is generated by the press actuation mechanisms 241 kdisposed below the pressing portions 241 g 2.

More specifically, referring to FIGS. 36A and 36B, downward movement ofthe pressing portions 241 g 2 causes the movement members 241 k 1provided in the press actuation mechanisms 241 k to be pushed down.Then, as shown in FIG. 36B, the developing cartridge urging springs 241k 3 are more compressed than the state shown in FIG. 36A. As thedeveloping cartridge urging springs 241 k 3 are compressed, elasticforce (energy) is generated in the developing cartridge urging springs241 k 3. With the elastic force, the upper wall 241 c of the developingframe 241 is urged downward.

Referring back to FIGS. 35A and 35B, as the upper wall 241 c of thedeveloping frame 241 is urged downward, the developing cartridge 240 isbrought into the pressing state, as shown in FIG. 35B from thenon-pressing state, as shown in FIG. 35A. In other words, the developingcartridge 240 is moved toward the photoconductive drum 252. The movementdirection of the developing cartridge 240 toward the photoconductivedrum 252 is the direction (guiding direction Z) that the collar member246 moves in the collar positioning accommodation base 251 a 2, as shownin FIG. 37B.

Referring to FIG. 37B, the pressing action line Y connecting thepressing position PP, which is the action point by the press actuationmechanisms 241 k, and the contact position (developing position) CP isparallel to the guiding direction Z. Therefore, with the elastic forcegenerated in the press actuation mechanisms 241 k, the developingcartridge 240 can be smoothly moved.

The angle formed between the developing cartridge pressing direction Xat the pressing position PP and the pressing action line Y is about 20degrees.

With such a structure, most of the elastic force applied at the pressingposition PP is transmitted to the contact position CP, withoutsignificant losses. Thus, a predetermined contact between the tonercarrying peripheral surface 244 b of the developing roller 244 and theimage carrying peripheral surface 252 b of the photoconductive drum 252may be reproduced stably. Further, the guide surfaces 241 m 1 of theguide projections 241 m are parallel to the guiding direction Z.Therefore, as shown in FIGS. 35A and 35B, the guide surfaces 241 m 1 ofthe guide projections 241 m may be properly pressed against thedeveloping cartridge insertion rollers 257. Thus, the movement of thedeveloping cartridge 240 along the guiding direction Z may be guidedsmoothly by the developing cartridge insertion rollers 257.

While the developing cartridge 240 is moved along the guiding directionZ from the non-pressing (retracted) position, as shown in FIG. 35A, tothe pressing position, as shown in FIG. 35B, the terminal portion 247 band the feeding member opposing portion 258 c 1, which is formedparallel to the pressing action line Y and the guiding direction Z,slide with each other. Therefore, developing bias voltage may be appliedbetween the developing roller 244 and the photoconductive drum 252, viathe developing bias terminal 258 and the terminal portion 257 b, forexample, from a time when the developing cartridge 240 is in thenon-pressing position.

As shown in FIG. 37B, the feeding member pressing direction S in whichthe terminal portion 247 b is pressed by the feeding member opposingportion 258 c 1 at their contact position is substantially perpendicularto the pressing action line Y and the guiding direction Z. With such astructure, a component of a feeding member pressing force by thedeveloping bias terminal 258 (feeding member opposing portion 258 c 1)parallel to the guiding direction Z is hardly generated. Therefore,contact between the toner carrying peripheral surface 244 b of thedeveloping roller 244 and the image carrying peripheral surface 252 b ofthe photoconductive drum 252 may be stabilized.

The feeding member opposing portion 258 c 1 is substantiallyperpendicular to the feeding member pressing direction S. With such astructure, a state where the feeding member pressing direction S issubstantially perpendicular to the pressing action line Y and theguiding direction Z may be stably realized.

(3) Installation of Process Cartridge

Referring to FIG. 39, the installation of the process cartridge 230 inthe main body casing 211 will be described below.

The side frame guide rollers 232 c and the rear beam guide rollers 234 bare inserted into a space behind the slide guide rollers 211 c 2disposed at the front ends of the slide guide frames 211 c, to place theside frame guide rollers 232 c and the rear beam guide rollers 234 b onthe slide rails 211 c 1. In this state, the slide guide rollers 211 c 2,the side frame guide rollers 232 c, and the rear beam guide rollers 234b are disposed between the slide rails 211 c 1 and the guide ribs 232 bof the side fames 232.

Then, as the process cartridge 230 is further pushed rearward, the slideguide rollers 211 c 2, the side frame guide rollers 232 c, and the rearbeam guide rollers 234 b rotate between the slide rails 211 c 1 and theguide ribs 232 b. Thus, the process cartridge 230 can be smoothly guidedinside the main body casing 211. At this time, the separation bosses 241f and the pressing bosses 241 g 1 disposed at the upper ends of thedeveloping cartridges 240 pass over the supporting frame upper plates219 b 2.

As the process cartridge 230 is further pushed rearward, the side frameguide rollers 232 c and the rear beam guide rollers 234 b pass throughthe slide rails 211 c 1 and the front ends of the guide ribs 232 b ofthe side frames 232 pass through the slide guide rollers 211 c 2, theprocess cartridge 230 slightly moves down. At this time, the slide rails211 c 1 and the guide ribs 232 b contact each other, and the separationbosses 241 f and the pressing bosses 241 g 1 move down into the bossaccommodating openings 219 b 5.

(4) Setting Positions of Developing Cartridge

Referring to FIG. 39, when the process cartridge 230 is installed in themain body casing 211, one of the bar cam members 219 a is moved in thefront-rear direction L by the drive source (not shown) provided in themain body casing 211. The pinion gear 219 c, which is engaged with therack gear 219 a 2 in the cam base end 219 a 1 of the one of the bar cammembers 219 a, rotates. In accordance with the rotation of the piniongear 219 c, the other pinion gear 219 c, which is connected to thepinion gear 219 c via the gear shaft 219 d, also rotates. The other barcam member 219 a engaged with the other pinion gear 219 c is moved.Thus, a pair of the bar cam members 219 a is moved in synchronizationwith each other, via a pair of the pinion gears 219 c and the gear shaft219 d. Accordingly, the developing cartridges 240 are set in either thepressing or non-pressing position. Referring to FIGS. 40 and 41, thepressing or non-pressing position of the developing cartridges 240 maybe determined by the positions of the bar cam members 219 a with respectto the front-rear direction L.

Referring to FIGS. 39 and 40, by setting the positions of the bar cammembers 219 a in the front-rear direction L, the supplementary cammembers 219 e disposed to face the boss accommodating openings 219 b 5are set to either the upright or turned state. The supplementary cammembers 219 e placed in the upright state protrude toward the bossaccommodating openings 219 b 5. Thus, the separation bosses 241 f areraised. As the supplementary cam members 219 e are maintained in theupright state, the separation bosses 241 are maintained raised. Thus,the developing cartridges 240 are held in the non-pressing (retracted)position.

Referring to FIGS. 39 and 41, pressing or non-pressing of the pressedbosses 241 g 1 with the pressing portions 219 a 8 may be determined bysetting the positions of the bar cam members 219 a in the front-reardirection L. As the pressed bosses 241 g 1 are pressed by the pressingportions 219 a 8, the developing cartridges 240 are urged downward andmoved to the pressing position.

(5) Selectively Urging Developing Cartridges

Referring to FIG. 39, the developing cartridges 240 (e.g., fourcartridges) are selectively urged downward in accordance with thepositions of the bar cam members 219 a in the front-rear direction L.The selective urging of the developing cartridges 240 will be describedin detail below.

(a) Linear Cam Mechanisms

First, the linear cam mechanisms 219 shown in FIG. 39 will be describedin detail below with reference to FIGS. 43A through 46.

Referring to FIGS. 43B and 44, when the bar cam members 219 a are placedin the rearmost position, the foremost supplementary cam members 219 e′and other supplementary cam members 219 e are all in the upright state,and contact the supplementary cam contact walls 219 a 6. The separationbosses 241 f are placed on the separation boss mounting slopes 219 e 3(219 e 3′) of the supplementary cam members 219 e (219 e′) placed in theupright state. The foremost and other pressing portions 219 a 8′, 219 a8 are all positioned behind the pressed bosses 241 g 1.

As the bar cam members 219 a are moved toward the front side from thestate shown in FIG. 44, the supplementary cam supporting portions 219 a5 (219 a 5′) move toward the front side while sliding with thesupplementary cam members 219 e (219 e′). At this time, thesupplementary cam members 219 e (219 e′) move rearward relative to thesupplementary cam supporting portions 219 a 5 (219 a 5′). Thesupplementary cam members 219 e (219 e′) do not move along thefront-rear direction L. Therefore, relative positions between thesupplementary cam members 219 e (219 e′) and the separation bosses 241 fwith respect to the front-rear direction L do not change. Further, asthe bar cam members 219 a move toward the front side, the tips of thepressing portions 219 a 8 (219 a 8′) approach the pressed bosses 241 g1.

The foremost protrusion 219 a 9′ first contacts the second supplementarycam projection 219 e 5′ of the supplementary cam member 219 e′. At thistime, the other protrusions 219 a 9 have not yet made contact with theother second supplementary cam projections 219 e 5 of the supplementarycam members 219 e. As the foremost protrusion 219 a 9′ contacts thesecond supplementary cam projection 219 e 5′, the foremost supplementarycam member 219 e′ pivotally moves in the clockwise direction in FIG. 44,resulting in the turned state, as shown in FIG. 45. In the turned state,the foremost supplementary cam member 219 e′ falls from thesupplementary cam supporting portion 219 a 5′ into the supplementary camexposure opening 219 a 7′. Thus, the rise of the separation bosses 241 glocated foremost is discontinued and the foremost separation bosses 241g are lowered.

Referring to FIG. 45, the tips of the only foremost pressing portions219 a 8′ are placed on the pressed bosses 241 g 1, which are locatedforemost. Thus, only the foremost pressed bosses 241 g 1 are selectivelypressed down.

As the bar cam members 219 a are further moved to the front side fromthe state shown in FIG. 45, the other protrusions 219 a 9 contact thesecond supplementary cam projections 219 e 5, so that the othersupplementary cam members 219 e are placed in the turned state and theother pressing portions 219 a 8 are placed on the pressed bosses 241 g1. Thus, all the separation bosses 241 f are lowered and all the pressedbosses 241 g 1 are pressed downward, as shown in FIG. 46.

As the bar cam members 219 a located at the foremost position, as shownin FIG. 46, start to move rearward, the first supplementary camprojections 219 e 4 of the three supplementary cam members 219 e otherthan the foremost supplementary cam member 219 e′ contact the ends ofthe supplementary cam supporting portions 219 a 5. The threesupplementary cam members 219 e are pivotally moved in thecounterclockwise direction in FIG. 46, so that the three supplementarycam members 219 e are placed in the upright state, as shown in FIG. 45.In the upright state, the separation boss mounting slopes 219 e 3provided on the top of the supplementary cam members 219 e oppose theseparation bosses 241 f. The supplementary cam members 219 e are placedon the supplementary cam supporting portions 219 a 5 in the uprightstate. Thus, the separation bosses 241 f are raised. At this time, theforemost supplementary cam members 219 e′ are still in the turned state.In other words, the foremost separation bosses 241 f have not yet beenraised by the foremost supplementary cam members 219 e′.

At the same time, the pressing portions 219 a 8 other than the foremostpressing portions 219 a 8′ are move away from the pressed bosses 241 g1. Thus, the pressing of the pressed bosses 241 g 1 with the pressingportions 219 a 8 is discontinued. At this time, the foremost pressingportions 219 a 8′ is still on the foremost pressed bosses 241 g 1. Thatis, the foremost pressed bosses 241 g 1 are being pressed down by theforemost pressing portions 219 a 8′.

As the bar cam members 219 a are further moved to the rear side from thestate shown in FIG. 45, the foremost supplementary cam members 219 e′are also placed in the upright state. The foremost pressing portions 219a 8′ are also moved away from the upper portions of the foremost pressedbosses 241 g 1. Thus, as shown in FIG. 44, all the separation bosses 241f are supported at higher positions and the pressing of the pressedbosses 241 g 1 are discontinued.

(b) Selective Urging of Developing Cartridges

The black developing cartridge 240K positioned foremost (right side inFIGS. 47-49) and other developing cartridges 240C, 240M, 240Y are urgeddownward differentially by the movement of the bar cam members 219 a andthe supplementary cam members 219 e, as shown in FIGS. 47 to 49

More specifically, as shown in FIG. 47, when the image forming operationis not performed, all the pressing portions 219 a 8 (including 219 a 8′)are away from the upper portions of the pressed bosses 241 g 1, so thatpressing of all the pressed bosses 241 g 1 are not conducted. Further,when the image forming operation is not performed, all the supplementarycam members 219 e (including 219 e′) are placed upright on thesupplementary cam supporting portions 219 a 5 (219 a 5′). Accordingly,all the separation bosses 241 f are held raised. Thus, the blackdeveloping cartridge 240K and other developing cartridges 240C, 240M,240Y are all placed in the non-pressing (retracted) position. Thus, allthe developing rollers 244 and the photoconductive drums 252 are spacedapart from each other when the image forming operation is not performed.

As shown in FIG. 48, when a monochrome image forming operation isperformed, the foremost pressing portion 219 a 8′ is placed on thepressed bosses 241 g 1 and the foremost supplementary cam members 219 e′are turned. Thus, in the foremost black developing cartridge 240K, thepressed bosses 241 g 1 are pressed down and rising of the separationbosses 241 f discontinues.

As the raising of the separation bosses 241 f is discontinued and thepressed bosses 241 g 1 are pressed down in the black developingcartridge 240K, the holding portion 241 g is slightly moved pivotallyabout the hinges 241 h in the clockwise direction in FIG. 48, asdescribed above. By the pivotal movement of the holding portion 241 g,the pressing portions 241 g 2 on the free end side of the holdingportion 241 g are moved downward. In accordance with the downwardmovement of the pressing portions 241 g 2, the press actuationmechanisms 241 k are pressed down to urge the developing frame 241downward. Thus, only the developing roller 244 of the black developingcartridge 240K makes contact with the relevant photoconductive drum 252.

As described above, when the monochrome image forming operation isperformed, the developing cartridges 240C, 240M, 240Y, other than theblack developing cartridge 240K are held in the non-pressing (retracted)position. Only the black developing cartridge 240K, which is used formonochrome image forming operation, is moved to the pressing position.

As shown in FIG. 49, when a full-color image forming operation isperformed, all the developing frames 241 are urged downward. Thus, theblack developing cartridge 240K and other developing cartridges 240C,240M, 240Y are all moved to the pressing position.

3. Effects According Structures of these Aspects

The color laser printer 210 according to this aspect may have thefollowing effects, other than those described above in conjunction withthe above aspects.

In this aspect, the electrode member 247 is pressed by the developingbias terminal 258 in the feeding member pressing direction Sperpendicular to the pressing action line Y connecting the pressingposition PP and the contact position CP. Accordingly, the contactbetween the developing roller 244 (toner carrying peripheral surface 244b) and the photoconductive drum 252 (image carrying peripheral surface252 b) at the contact position CP may be stabilized. Further, powerfeeding to the developing roller 244 may be performed stably by thedeveloping bias terminal 258, via the electrode member 247. Thus,according to this aspect, an image may be formed favorably.

In this aspect, as the feeding member opposing portion 258 c 1 formedsubstantially parallel to the pressing action line Y and the terminalportion 247 b contact each other, electrical connection between theterminal portion 247 b and the developing bias terminal 258 is made.Thus, a line normal to the feeding member opposing portion 258 c 1 atthe feeding member pressing position SP where the terminal portion 247 bcontacts the feeding member opposing portion 258 c 1 may be set stablyto the direction substantially perpendicular to the pressing action lineY. Therefore, the developing bias terminal 258 and the electrode member247 that make the feeding member pressing direction S substantiallyperpendicular to the pressing action line Y, may be achieved with simplestructures.

In this aspect, the feeding member opposing portion 258 c 1 issubstantially parallel to the collar positioning accommodation base 251a 2 (guiding direction Z). Therefore, when the collar member 246 movesin the collar positioning accommodation base 251 a 2 along the pressingaction line Y, the feeding member opposing portion 258 c 1 and theterminal portion 247 b are relatively moved along the pressing actionline Y and the guiding direction Z while contacting with other.Accordingly, the toner carrying peripheral surface 244 b of thedeveloping roller 244 and the image carrying peripheral surface 252 b ofthe photoconductive drum 252 may be brought into a predetermined contactwith each other, and a power feedable condition from the developing biasterminal 258 to the developing roller 244 may be ensured.

In this aspect, the terminal portion 247 b intersects the pressingaction line Y when viewed from the direction perpendicular to thefeeding member pressing direction S and the pressing action line Y.

In this aspect, the position (feeding member pressing position SP) wherethe electrode member 247 and the developing bias terminal 258 contacteach other, overlaps with or disposed within an area of the couplingpart guide groove 251 e (coupling accommodation base 251 e 2) thatreceives therein the coupling part 248 a (input opening portion 248 a2), when viewed from the side along the width direction W. Further, inthis aspect, the feeding member pressing position SP is within an areadefined by the outside diameter of the input opening portion 248 a 2. Inthis aspect, the feeding member pressing position SP substantiallycorresponds to the axis of the driven coupling part 248 a 1 and thecoupling drive gear 283.

Thus, the drive force may be transmitted reliably and stably to thedeveloping cartridge 240 from the drive force transmission mechanism280, via the coupling drive gear 283 and the coupling part 248 a. At thesame time, contact between the developing roller 244 and thephotoconductive drum 252 at the contact position CP and power feedingfrom the developing bias terminal 258 to the developing roller 244 viathe electrode member 247 may be stabilized.

When the color member 248 is moved in the collar positioningaccommodation base 251 a 2 along the pressing action line Y, the guidesurfaces 241 m 1 of the guide projections 241 m formed substantiallyparallel to the pressing action line Y contact the developing cartridgeinsertion rollers 257 rotatably supported at the bottom wall 251 b.

Therefore, the movement of the collar member 246 and the terminalportion 247 b may be smoothly guided along the pressing action line Ywhen the developing cartridge 240 is installed in the process cartridgeframe 230 a (drum frame 251), according to the structures of thisaspect. Thus, while the developing cartridges 240 are smoothly installedin the process cartridge frame 230 a, the favorable electricalconnection may be established between the developing bias terminal 258and the electrode member 247 and the stable contact may be made betweenthe toner carrying peripheral surface 244 b of the developing roller 244and the photoconductive drum 252 at the contact position CP

In this aspect, the angle formed between the developing cartridgepressing direction X and the pressing action line Y is set to about 20degrees. Thus, the guide surfaces 241 m 1 of the guide projections 241 mare pressed against the developing cartridge insertion rollers 257 at apredetermined pressure, without applying extremely strong or weakpressures thereto. The elastic force of the developing cartridge urgingsprings 241 k 3 may be transmitted to the contact position CP withoutsignificant losses.

Accordingly, while favorable contact between the developing cartridgeinsertion rollers 257 and the guide surfaces 241 m 1 is maintained, thedeveloping cartridge insertion rollers 257 may smoothly rotate. Thus,the developing cartridge 240 can be smoothly guided along the guidingdirection Z by the developing cartridge insertion rollers 257.Therefore, the predetermined contact between the toner carryingperipheral surface 244 b of the developing roller 244 and the imagecarrying peripheral surface 252 b of the photoconductive drum 252 may bereliably and stably achieved at the contact position CP.

In this aspect, the developing cartridge 240 may be positioned using thecollar member 246 covering the developing roller shaft 244 a from itsoutside. Thus, the positioning between the developing cartridge 240 andthe process cartridge frame 230 a (drum frame 251) may be performed nearthe developing roller shaft 244 a. Therefore, the predetermined contactbetween the developing roller 244 and the photoconductive drum 252 maybe reliably made at the contact position CP with a simple structure.

In this aspect, when the developing cartridge 240 is installed in theprocess cartridge frame 230 a, the collar member 246 of the developingcartridge 240 may be received in the collar positioning guide groove 251a 1 of the drum frame 251. Then, the collar member 246 may reach thecollar positioning accommodation base 251 a 2 formed at a lower end ofthe collar positioning guide groove 251 a 1. At this time, the collarmember 246 may move along the pressing action line Y in the collarpositioning accommodation base 251 a 2. When the collar member 246reaches a predetermined position in the collar positioning accommodationbase 251 a 2, the positioning between the developing cartridge 240 andthe process cartridge frame 230 a (drum frame 251) may be performed.

With such a structure, the positioning between the developing cartridge240 and the process cartridge frame 230 a when the developing cartridge240 is installed in the process cartridge frame 230 a may be performedsmoothly and reliably. Therefore, the favorable electrical connectionbetween the developing bias terminal 258 and the electrode member 247and the reliable positioning between the developing roller 244 and thephotoconductive dram 252 may be stably achieved.

Further, in this aspect, while rotatably supporting the developingroller shaft 244 a and the supply roller shaft 243 a, the electrodemember 247 may electrically connect the developing roller shaft 244 aand the supply roller shaft 243 a. Thus, power may be supplied to thesupply roller 243 and the developing roller 244, via the developing biasterminal 258 and the electrode member 247, such that the supply roller243 and the developing roller 244 become at substantially the samepotential. Therefore, while the predetermined contact between the tonercarrying peripheral surface 244 b of the developing roller 244 and thephotoconductive drum 252 is formed at the contact position CP, the powersupply to the supply roller 243 and the developing roller 244 may bestably achieved, such that the supply roller 243 and the developingroller 244 become at substantially the same potential.

In this aspect, the collar member 246 having the cylindrical outer shapewhen viewed from a side along the width direction W extends from one endof the developing frame 241 with respect to the width direction W. Thecoupling part 248 a (input opening portion 248 a 2) having a greateroutside diameter than the collar member 246 extends from the other endof the developing frame 241 with respect to the width direction W. Thecoupling part guide groove 251 e 1 is formed wider enough to receive thecoupling part 248 a than the collar positioning guide groove 251 a 1.

With such a structure, even when the collar member 246 is inserted intothe coupling part guide groove 251 e 1 and the coupling part 248 a(input opening portion 248 a 2) is tried to be inserted into the collarpositioning guide groove 251 a 1, the coupling part 248 a may not beproperly inserted into the collar positioning guide groove 251 a 1, dueto the differences between their outside shapes. More specifically, thecoupling part 248 a (input opening portion 248 a 2) having the greateroutside diameter cannot be inserted into the collar positioning guidegroove 251 a 1 formed into a width suitable for the collar member 246having the smaller outside diameter.

Accordingly, the improper installation of the developing cartridge 240in the process cartridge frame 230 a (drum frame 251) may be favorablyprevented with such a structure.

Further, with the structure, the drive coupling part 281 can beshortened by the length that the coupling part 248 a (input openingportion 248 a 2) extended from the process cartridge frame 230 a.Therefore, the size of the drive force transmission mechanism 280provided in the main body casing 211 can be reduced with respect to thewidth direction W. Consequently, the color laser printer 210 may bedownsized.

Further, in this aspect, the developing cartridge 240 may be urgedtoward the photoconductive drum 252 by the holding portion 241 g and thepress actuation mechanisms 241 k provided on the upper wall 241 c of thedeveloping frame 241. Thus, the urging of the developing roller 244toward the contact position CP may be achieved with such a simplestructure.

The bar cam members 219 a provided in the linear cam mechanisms 219 aremoved in the front-rear direction L along which the developingcartridges 240 are arranged, so that the pressed bosses 241 g 1 and thepressing portions 241 g 2 may be selectively moved toward the developingcartridge urging springs 241 k 3. With such a structure, only thedeveloping cartridge(s) 240 used for the image forming operation may beurged toward the contact position CP. Thus, deterioration or wear of thedeveloping roller 244, for example, due to a continuous slide betweenthe developing roller 244 and the photoconductive drum 252 for a longperiod of time, may be effectively reduced with such a simple structure.

D. Implication of Variations and Modifications

While the invention has been described in connection with specificaspects, it will be understood by those skilled in the art that othervariations and modifications of the aspects described above may be madewithout departing from the scope of the invention. Other aspects will beapparent to those skilled in the art from a consideration of thespecification or practice of the invention disclosed herein. It isintended that the specification and the described examples only areconsidered as exemplary of the invention, with the true scope of theinvention being defined by the following claims.

Image forming apparatuses of the invention are not limited toelectrophotographic image forming apparatuses. Further, when theinvention is applied to an electrophotographic image forming apparatus,the image forming apparatus is not limited to a laser printer.

The structures of the above aspects may be replaced by otherimplementations not described or combined.

The color laser printer 210 may be structured such that thephotoconductive drum 252 may be directly supported by the processcartridge frame 230 a and the developing cartridges 240 may be directlyremoved from or installed in the process cartridge frame 230 a, withouthaving the drum frame 251 in certain aspects.

In at least one aspect, the drum unit 50 may be removably disposed inthe process cartridge frame 230 a.

In at least some aspects, even when the feeding member pressing positionSP does not substantially match with the axes of the driven couplingpart 248 a 1 and the coupling drive gear 283, the driven coupling part248 a 1 of the coupling part 248 a or the drive coupling drive gear 283may be formed such that areas defined by their outer shapes overlap orinclude the feeding member pressing position SP when viewed from alongthe longitudinal direction of the developing cartridge 240, as shown inFIG. 52. With such an illustrative structure, effects of the inventionmay be achieved successfully.

While this disclosure has been described in conjunction with theexemplary aspects outlined above, various alternatives, modifications,variations, improvements and/or substantial equivalents, whether knownor may be presently unforeseeable, may become apparent to those havingat least ordinary skill in the art. Accordingly, the exemplary aspectsof the disclosure, as set forth above, are intended to be illustrative,not limiting. Various changes may be made without departing from thespirit and scope of the disclosure. Therefore, the disclosure isintended to embrace all known or later developed alternatives,modifications, variations, improvements and/or substantial equivalents.

What is claimed is:
 1. A developing cartridge comprising: a caseincluding a first sidewall and a second sidewall opposite to the firstsidewall; a developing roller disposed between the first sidewall andthe second sidewall, the developing roller being configured to rotateabout a first axis line; an electrode for applying developing bias tothe developing roller, the electrode being positioned at the firstsidewall, the electrode including a contact point; and a driven couplingpositioned at the second sidewall, the driven coupling being configuredto rotate about a second axis line, the driven coupling including: afirst cylindrical portion substantially hollowed and provided with aninner peripheral surface, the first cylindrical portion including adriven part which extends radially inward from the inner peripheralsurface, and a second cylindrical portion concentrically disposed withthe first cylindrical portion, the second cylindrical portion includinga gear, wherein the contact point of the electrode is disposed within aplane of projection when the driven coupling is projected in a directionparallel to the second axis line towards the electrode, the plane ofprojection being defined by projecting the first cylindrical portion ofthe driven coupling in the direction parallel to the second axis linetowards the electrode.